单位换算

单位换算是指通过乘以换算系数实现不同计量单位间的等量换算。

换算技术

过程

单位换算过程与用户具体情况和预期目的相关。可能受法令、合同、技术规格或其它出版物技术标准的限制。工程判断可能包括以下因素:

• 计量准确与精密度与相关测量的不准确度
• 初始量测统计置信区间或容许区间
• 计量有效数字位数
• 包括工程容差计量的预期用途

某些从一个单位系统需要不增减精度地向另一个单位体系严密转换第一个量度。有时被称为“软转换”。它不涉及更改被计量的物理配置。

与之相比，“硬转换”或“适应转换”可能不完全相等。它更改计量以适合在新体系内的有效数字与单位。它有时涉及项目的稍微不同的配置或尺寸替代。有时允许并使用标称值。

换算系数

此条目内不列出在公制单位国际单位制词头间的转换（例如：1 千克 = 1000 克, 1 毫克 = 0.001 克）。除非单位还有其他常见名称。

表格次序

各表内的单位以其英文字词的字母顺序列出，突出显示SI单位（基本单位或导出单位）。

换算系数表

此条目给出列于索引内的各个物理量数值转换系数列表。各物理量不同单位的数值以相应的SI术语表示并显示（某些仅有历史意义）。

图例

符号	定义
≡	严格等于
≈	近似等于
数字	表示数字无限循环（例如8.294369表示8.294369369369369…）
（H）	过去使用

长度

长度

单位名称	符号	定义	与SI单位的关系
埃	Å	≡ $1 \times 10^{-10}$m	≡ 0.1 nm
天文单位	AU	≡ 149597870700 m ≈ 地球与太阳之间的距离	≡ 149597870700 m
Barleycorn（H）		= $\frac{1}{3}$in（参见上面关于舍入的说明）	≈ $8.4\overline{6} \times 10^{-3}$m
玻尔，原子长度单位	a0	≡ 氢的玻尔半径	≈ $5.291\ 772\ 085\ 9 \times 10^{-11}\pm 3.6 \times 10^{-20}$m
链（英制）(cable length)		≡ 608 ft	≈ 185.3184 m
链（国际）(cable length)		≡ $\frac{1}{10}$ 海里	≡ 185.2 m
链（美国）(cable length)		≡ 720 英尺	= 219.456 m
测链 (chain)	ch	≡ 66英尺（美国） ≡ 4 竿 (单位)	≈ 7001201168400000000♠20.11684 米
腕尺、肘(cubit)（H）		≡ 从手指到肘部的距离 ≈ 18 in	≈ 0.5 m
厄尔（H）	ell	≡ 45 in （通常在英格兰使用）	= 1.143 m
㖊	fm	≡ 6 ft	= 1.8288 m
飞米	fm	≡ 6985100000000000000♠1×10−15 米	≡ 6985100000000000000♠1×10−15 米
finger（长度单位）		≡ $\frac{7}{8}$in	= 6998222250000000000♠0.022225 米
finger（长度单位）（服装）		≡ $4\frac{1}{2}$in	= 0.1143 m
英尺 (Benoît)（H）	ft (Ben)		≈ 6999304799735000000♠0.304799735 米
英尺 (Cape)（H）		于1859年由法律规定为1.033英国英尺	≈ 6999314858000000000♠0.314858 米
英尺 (Clarke's)（H）	ft (Cla)		≈ 6999304797265400000♠0.3047972654 米
英尺（印度）（H）	ft Ind		≈ 6999304799514000000♠0.304799514 米
英尺（国际）	ft	≡ 0.3048 m ≡ $\frac{1}{3}$yd ≡ 12 英寸	≡ 0.3048 m
英尺 (Sear's)（H）	ft (Sear)		≈ 6999304799470000000♠0.30479947 米
英尺（美国测量）	ft（美国）	≡ $\frac{1200}{3937}$m	≈ 6999304800610000000♠0.304800610 米
french; charriere	F	≡ $\frac{1}{3}$mm	= $0.\overline{3} \times 10^{-3}$m
浪	fur	≡ 10 测链 = 660 ft = 220 yd	= 201.168 m
hand		≡ 4 in	≡ 0.1016 m
英寸（国际）	in	≡ 2.54 cm ≡ $\frac{1}{36}$yd ≡ $\frac{1}{12}$ft	≡ 0.0254 m
里格 (land)	lea	≡ 3 美制英里	= 4828.032 m
光日		≡ 24 光时	≡ 7013259020683712000♠2.59020683712×1013 米
光时		≡ 60 光分	≡ 7012107925284880000♠1.0792528488×1012 米
光分		≡ 60 光秒	≡ 7010179875474800000♠1.798754748×1010 米
光秒		≡ 光在真空中1秒走过的距离	≡ 299792458 m
光年	ly	≡ 光在真空中365.25天走过的距离	= 7015946073047258080♠9.4607304725808×1015 米
line	ln	≡ $\frac{1}{12}$in	= $0.002\ 11\overline{6}$m
link (Gunter's; Surveyor's)	lnk	≡ $\frac{1}{100}$ch ≡ 0.66 ft ≡ 7.92 in 测链 (chain) 上组成链的环节 (link)，下同	= 6999201168000000000♠0.201168 米
link (Ramsden's; Engineer's)	lnk	≡ 1 ft	= 0.3048 m
米（国际单位制基本单位）	m	≡ 光在真空中$\frac{1}{299\ 792\ 458}$秒走过的距离 ≈ 赤道至南极点或北极点距离的$\frac{1}{100\ 000\ 00}$	≡ 1 m
mickey		≡ $\frac{1}{200}$in	= 6996127000000000000♠1.27×10−4 米
微米	µ		≡ 6994100000000000000♠1×10−6 米
密耳 (mil; thou)	mil	≡ 6995254000000000000♠1×10−3 英寸	≡ 6995254000000000000♠2.54×10−5 米
挪威/瑞典密耳	mil	≡ 10 km	= 10000 m
地理英里（H）		≡ 6082 ft	= 1853.7936 m
英里（国际）	mi	≡ 80 测链 ≡ 5280 ft ≡ 1760 yd	≡ 1609.344 m
英里（战术或数据）		≡ 6000 ft	≡ 1828.8 m
英里（电报）（H）	mi	≡ 6087 ft	= 1855.3176 m
英里 (美国测量)	mi	≡ 5280 美国测量英尺 ≡ ($5280 \times \frac{1200}{3937}$) m	≈ 1609.347219 m
nail（服装）		≡ $2\frac{1}{4}$in	= 0.057 15 m
纳米	nm	≡ 6991100000000000000♠1×10−9 米	≡ 6991100000000000000♠1×10−9 米
海里格 (nautical league)	NL; nl	≡ 3 nmi	= 5556 m
海里 (Admiralty)	NM (Adm); nmi (Adm)	= 6080 ft	= 1853.184 m
海里（国际）	NM; nmi	≡ 1852 m	≡ 1852 m
海里（美国1954年前）		≡ 1853.248 m	≡ 1853.248 m
pace		≡ 2.5 ft	= 0.762 m
plam		≡ 3 in	= 0.0762 m
秒差距	pc	与一个天文单位为一弧秒视差移位的恒星距离	≈ $3.085\ 677\ 82 \times 10^{16} \pm 6 \times 10^6$m
皮卡、派卡 (pica)		≡ 12 点	由点量度决定。
点（美英）	pt	≡ $\frac{1}{72.272}$in	≈ 0.000 351 450 m
点 (Didot; 欧洲)	pt	≡ $\frac{1}{12} \times \frac{1}{72}$of pied du roi; 1878年后: ≡ $\frac{5}{133}$cm	≈ 0.000 375 97 m; 1878年后: ≈ 0.000 375 939 85 m
点 (PostScript)	pt	≡ $\frac{1}{72}$in	= $0,000\ 352 \ \overline{7}$m
点 (TeX)	pt	≡ $\frac{1}{72.27}$in	= $0.00\overline{0\ 351\ 459\ 8}$m
quarter		≡ $\frac{1}{4}$yd	= 0.2286 m
杆 (rod; pole; perch)（H）	rd	≡ $16\frac{1}{2}$ft	= 5.0292 m
Rope（H）	rope	≡ 20 ft	= 6.096 m
span（H）		≡ 9 in	= 0.2286 m
spat			≡ 1×1012 m
stick（H）		≡ 2 in	= 0.0508 m
stigma; bicron (皮米)	pm		≡ 1×10−12 m
缇 (twip)	twp	≡ $\frac{1}{1440}$in	= $1.763\overline{8} \times 10^{-5}$m
x unit; siegbahn	xu		≈ 1.0021×10−13 m
码（国际）	yd	≡ 0.9144 m ≡ 3 ft ≡ 36 in	≡ 0.9144 m

面积

面积

单位名称	符号	定义	与SI单位的关系
英亩（国际）	ac	≡ 1浪 × 1链 = 4840 平方码	≡ 4 046.856 4224 m2
英亩（美国测量）	ac	≡ 10 sq ch = 4840 平方码或43560平方呎	≈ 4 046.873 m2
公亩	a	≡ 100 m2	= 100 m2
靶恩	b	≡ 10−28 m2	= 10−28 m2
barony		≡ 4000 ac	≈ 1.618 742×107 m2
board	bd	≡ 1 in × 1 ft	= 7.741 92×10−3 m2
boiler horsepower equivalent direct radiation	bhp EDR	≡ $\frac{(1\ \text{ft}^2)(1\ \text{bhp})}{(240\ \text{BTU}_\text{IT}/\text{h})}$	≈ 12.958 174 m2
圆英寸	circ in	≡ $\frac{\pi}{4}$sq in	≈ 5.067 075×10−4 m2
圆密耳	circ mil	≡ $\frac{\pi}{4}$mil2	≈ 5.067 075×10−10 m2
cord		≡ 192 bd	= 1.486 448 64 m2
dunam		≡ 1 000 m2	= 1 000 m2
guntha		≡ 121 sq yd	≈ 101.17 m2
公顷	ha	≡ 10 000 m2	≡ 10 000 m2
hide		≈ 120 ac (variable)	≈ 5×105 m2
rood	ro	≡ $\frac{1}{4}$ac	= 1 011.714 1056 m2
section		≡ 1 mi × 1 mi	= 2.589 988 110 336×106 m2
shed		≡ 10−52 m2	= 10−52 m2
square (roofing)		≡ 10 ft × 10 ft	= 9.290 304 m2
平方测链（国际）	sq ch	≡ 66 ft × 66 ft = 1/10 ac	≡ 404.685 642 24 m2
平方测链（美国测量）	sq ch	≡ 66 ft（美国）× 66 ft（美国）= $\frac{1}{10}$ac	≈ 404.687 3 m2
平方英尺	sq ft	≡ 1 ft × 1 ft	≡ 9.290 304×10−2 m2
平方英尺（美国测量）	sq ft	≡ 1 ft（美国）× 1 ft（美国）	≈ 9.290 341 161 327 49×10-2 m2
平方英寸	sq in	≡ 1 in × 1 in	≡ 6.4516×10−4 m2
平方千米	km2	≡ 1 km × 1 km	= 106 m2
square link (Gunter's)（国际）	sq lnk	≡ 1 lnk × 1 lnk ≡ 0.66 ft × 0.66 ft	= 4.046 856 4224×10−2 m2
square link (Gunter's)(US Survey)	sq lnk	≡ 1 lnk × 1 lnk ≡ 0.66 ft（美国） × 0.66 ft（美国）	≈ 4.046 872×10−2 m2
square link (Ramsden's)	sq lnk	≡ 1 lnk × 1 lnk ≡ 1 ft × 1 ft	= 0.09290304 m2
平方米 (SI unit)	m2	≡ 1 m × 1 m	= 1 m2
平方密尔	sq mil	≡ 1 mil × 1 mil	= 6.4516×10−10 m2
平方英里	sq mi	≡ 1 mi × 1 mi	= 2.589 988 110 336×106 m2
平方英里（美国测量）	sq mi	≡ 1 mi（美国）× 1 mi（美国）	≈ 2.589 998 47×106 m2
square rod/pole/perch	sq rd	≡ 1 rd × 1 rd	= 25.292 852 64 m2
平方码（国际）	sq yd	≡ 1 yd × 1 yd	≡ 0.836 127 36 m2
stremma		≡ 1 000 m2	= 1 000 m2
township		≡ 36 sq mi（美国）	≈ 9.323 994×107 m2
yardland		≈ 30 ac	≈ 1.2×105 m2

体积

体积

单位	符号	定义	与SI单位的关系
英亩英尺	ac ft	≡ 1 ac x 1 ft = 43 560 ft3	= 1 233.481 837 547 52 m3
英亩-英寸		≡ 1 ac × 1 in	= 102.790 153 128 96 m3
barrel（英制）	bl (imp)	≡ 36 gal (imp)	= 0.163 659 24 m3
barrel (petroleum)	bl; bbl	≡ 42 gal（美国）	= 0.158 987 294 928 m3
barrel (US dry)	bl（美国）	≡ 105 qt（美国）= $\frac{105}{32}$bu (US lvl)	= 0.115 628 198 985 075 m3
barrel (US fluid)	fl bl（美国）	≡ $31\frac{1}{2}$gal（美国）	= 0.119 240 471 196 m3
board-foot	fbm	≡ 144 cu in	≡ 2.359 737 216×10−3 m3
bucket（英制）	bkt	≡ 4 gal (imp)	= 0.018 184 36 m3
bushel（英制）	bu (imp)	≡ 8 gal (imp)	= 0.036 368 72 m3
bushel (US dry heaped)	bu（美国）	≡ $1\frac{1}{4}$bu (US lvl)	= 0.044 048 837 7086 m3
bushel (US dry level)	bu (US lvl)	≡ 2 150.42 cu in	= 0.035 239 070 166 88 m3
butt, pipe		≡ 126 gal (wine)	= 0.476 961 884 784 m3
coomb		≡ 4 bu (imp)	= 0.145 474 88 m3
cord (firewood)		≡ 8 ft × 4 ft × 4 ft	= 3.624 556 363 776 m3
cord-foot		≡ 16 cu ft	= 0.453 069 545 472 m3
立方英寻	cu fm	≡ 1 fm × 1 fm × 1 fm	= 6.116 438 863 872 m3
立方英尺	cu ft	≡ 1 ft × 1 ft × 1 ft	≡ 0.028 316 846 592 m3
立方英寸	cu in	≡ 1 in × 1 in × 1 in	≡ 16.387 064×10−6 m3
立方米（SI单位）	m3	≡ 1 m × 1 m × 1 m	≡ 1 m3
立方英里	cu mi	≡ 1 mi × 1 mi × 1 mi	≡ 4 168 181 825.440 579 584 m3
立方码	cu yd	≡ 27 cu ft	≡ 0.764 554 857 984 m3
杯 (breakfast)		≡ 10 fl oz (imp)	= 284.130 625×10−6 m3
杯 (加拿大)	c (CA)	≡ 8 fl oz (imp)	= 227.3045×10−6 m3
cup（公制）	c	≡ 250.0×10−6 m3	= 250.0×10−6 m3
cup (US customary)	c（美国）	≡ 8 US fl oz ≡ $\frac{1}{16}$gal（美国）	= 236.588 2365×10−6 m3
杯（美国食品营养标签）	c（美国）	≡ 240 mL	= 6996240000000000000♠2.4×10−4 m3
dash（英制）		≡ $\frac{1}{384}$gi (imp) = $\frac{1}{2}$pinch (imp)	= $396.961\ 751\ 302\ 08\overline{3} \times 10^{-9}$m3
dash（美国）		≡ $\frac{1}{96}$US fl oz = $\frac{1}{2}$US pinch	= 308.057 599 609 375×10−9 m3
dessertspoon（英制）		≡ $\frac{1}{12}$gi (imp)	= $11.838\ 776\ 041\overline{6} \times 10^{-6}$m3
drop（英制）	gtt	≡ $\frac{1}{288}$fl oz (imp)	= $98.656\ 467\ 013\ \overline{8} \times 10^{-9}$m3
drop（英制）(alt)	gtt	≡ $\frac{1}{1824}$gi (imp)	≈ 77.886 684×10−9 m3
drop (medical)		≡ $\frac{0.9964}{12}$ml	= $83.0\overline{3} \times 10^{-9}$m3
drop (medical)		≡ $\frac{1}{12}$ml	= $83.\overline{3} \times 10^{-9}$m3
drop（公制）		≡ $\frac{1}{20}$mL	= 50.0×10−9 m3
drop（美国）	gtt	≡ $\frac{1}{360}$US fl oz	= $82.148\ 693\ 229\ \overline{16} \times 10^{-9}$m3
drop（美国）(alt)	gtt	≡ $\frac{1}{456}$US fl oz	≈ 64.854 231 496 71×10−9 m3
drop（美国）(alt)	gtt	≡ $\frac{1}{576}$US fl oz	≈ 51.342 933 268 23×10−9 m3
fifth		≡ $\frac{1}{5}$US gal	= 757.082 3568×10−6 m3
firkin		≡ 9 gal（美国）	= 0.034 068 706 056 m3
fluid drachm（英制）	fl dr	≡ $\frac{1}{8}$fl oz (imp)	= 3.551 632 8125×10−6 m3
fluid dram（美国）; US fluidram	fl dr	≡ $\frac{1}{8}$US fl oz	= 3.696 691 195 3125×10−6 m3
fluid scruple（英制）	fl s	≡ $\frac{1}{24}$fl oz (imp)	= $1.183\ 877\ 604\ 1\overline{6} \times 10^{-6}$m3
gallon (beer)	beer gal	≡ 282 cu in	= 4.621 152 048×10−3 m3
gallon（英制）	gal (imp)	≡ 4.546  09 L	≡ 4.546 09×10−3 m3
gallon (US dry)	gal（美国）	≡ $\frac{1}{8}$bu (US lvl)	= 4.404 883 770 86×10−3 m3
gallon (US fluid; Wine)	gal（美国）	≡ 231 cu in	≡ 3.785 411 784×10−3 m3
gill（英制）; Noggin	gi (imp); nog	≡ 5 fl oz (imp)	= 142.065 3125×10−6 m3
gill（美国）	gi（美国）	≡ 4 US fl oz	= 118.294 118 25×10−6 m3
hogshead（英制）	hhd (imp)	≡ 2 bl (imp)	= 0.327 318 48 m3
hogshead（美国）	hhd（美国）	≡ 2 fl bl（美国）	= 0.238 480 942 392 m3
jigger (bartending)		≡ $1\frac{1}{2}$US fl oz	≈ 44.36×10−6 m3
kilderkin		≡ 18 gal (imp)	= 0.081 829 62 m3
lambda	λ	≡ 1 mm3	= 1×10−9 m3
last		≡ 80 bu (imp)	= 2.909 4976 m3
litre	L	≡ 1 dm3	≡ 0.001 m3
load		≡ 50 cu ft	= 1.415 842 3296 m3
minim（英制）	min	≡ $\frac{1}{480}$fl oz (imp) = $\frac{1}{60}$fl dr (imp)	= 59.193 880 208 3×10−9 m3
minim（美国）	min	≡ $\frac{1}{480}$US fl oz = $\frac{1}{60}$US fl dr	= 61.611 519 921 875×10−9 m3
盎司（英制）	fl oz (imp)	≡ $\frac{1}{160}$gal (imp)	≡ 28.413 0625×10−6 m3
盎司（美制）	US fl oz	≡ $\frac{1}{128}$gal（美国）	≡ 29.573 529 5625×10−6 m3
盎司 (fluid US food nutrition labeling)	US fl oz	≡ 30 mL	≡ 6995300000000000000♠3×10−5 m3
peck（英制）	pk	≡ 2 gal (imp)	= 9.092 18×10−3 m3
peck (US dry)	pk	≡ $\frac{1}{4}$US lvl bu	= 8.809 767 541 72×10−3 m3
perch	per	≡ $16\frac{1}{2}$ft × $1\frac{1}{2}$ft × 1 ft	= 0.700 841 953 152 m3
pinch（英制）		≡ $\frac{1}{192}$gi (imp) = $\frac{1}{8}$tsp (imp)	= 739.923 502 60416×10−9 m3
pinch（美国）		≡ $\frac{1}{48}$US fl oz = $\frac{1}{8}$US tsp	= 616.115 199 218 75×10−9 m3
pint（英制）	pt (imp)	≡ $\frac{1}{8}$gal (imp)	= 568.261 25×10−6 m3
pint (US dry)	pt (US dry)	≡ $\frac{1}{64}$bu (US lvl) ≡ $\frac{1}{8}$gal (US dry)	= 550.610 471 3575×10−6 m3
pint (US fluid)	pt (US fl)	≡ $\frac{1}{8}$gal（美国）	= 473.176 473×10−6 m3
pony		≡ $\tfrac{3}{4}$US fl oz	= 22.180 147 171 875×10−6 m3
pottle; quartern		≡ $\frac{1}{2}$gal (imp) = 80 fl oz (imp)	= 2.273 045×10−3 m3
quart（英制）	qt (imp)	≡ $\frac{1}{4}$gal (imp)	= 1.136 5225×10−3 m3
quart (US dry)	qt（美国）	≡ $\frac{1}{32}$bu (US lvl) = $\frac{1}{4}$gal (US dry)	= 1.101 220 942 715×10−3 m3
quart (US fluid)	qt（美国）	≡ $\frac{1}{4}$gal (US fl)	= 946.352 946×10−6 m3
quarter; pail		≡ 8 bu (imp)	= 0.290 949 76 m3
register ton		≡ 100 cu ft	= 2.831 684 6592 m3
sack（英制）; bag		≡ 3 bu (imp)	= 0.109 106 16 m3
sack（美国）		≡ 3 bu (US lvl)	= 0.105 717 210 500 64 m3
seam		≡ 8 bu (US lvl)	= 0.281 912 561 335 04 m3
shot		≡ 1 US fl oz	≈ 29.57×10−6 m3
strike（英制）		≡ 2 bu (imp)	= 0.072 737 44 m3
strike（美国）		≡ 2 bu (US lvl)	= 0.070 478 140 333 76 m3
tablespoon (Australian metric)			≡ 20.0×10−6 m3
tablespoon (Canadian)	tbsp	≡ $\frac{1}{2}$fl oz (imp)	= 14.206 531 25×10−6 m3
tablespoon（英制）	tbsp	≡ $\frac{5}{8}$fl oz (imp)	= 17.758 164 0625×10−6 m3
tablespoon（公制）			≡ 15.0×10−6 m3
tablespoon (US customary)	tbsp	≡ $\frac{1}{2}$US fl oz	= 14.786 764 7825×10−6 m3
tablespoon (US food nutrition labeling)	tbsp	≡ 15 mL	= 6995150000000000000♠1.5×10−5 m3
teaspoon (Canadian)	tsp	≡ $\frac{1}{16}$fl oz (imp)	= 4.735 510 416×10−6 m3
teaspoon（英制）	tsp	≡ $\frac{1}{24}$gi (imp)	= 5.919 388 02083×10−6 m3
teaspoon（公制）		≡ 5.0×10−6 m3	= 5.0×10−6 m3
teaspoon (US customary)	tsp	≡ $\frac{1}{6}$US fl oz	= 4.928 921 595×10−6 m3
teaspoon (US food nutrition labeling)	tsp	≡ 5 mL	= 6994499999999999999♠5×10−6 m3
timber foot		≡ 1 cu ft	= 0.028 316 846 592 m3
ton (displacement)		≡ 35 cu ft	= 0.991 089 630 72 m3
ton (freight)		≡ 40 cu ft	= 1.132 673 863 68 m3
ton (water)		≡ 28 bu (imp)	= 1.018 324 16 m3
tun		≡ 252 gal (wine)	= 0.953 923 769 568 m3
wey（美国）		≡ 40 bu (US lvl)	= 1.409 562 806 6752 m3

平面角

平面角

单位名称	符号	定义	与SI单位的关系
角密耳	µ	≡ $\frac{2\pi}{6400}$rad	≈ 0.981 748×10-3 rad
弧分; MOA	'	≡ $\frac{1^\circ}{60}$	≈ 0.290 888×10-3 rad
弧秒	"	≡ $\frac{1^\circ}{3600}$	≈ 4.848 137×10-6 rad
centesimal minute of arc	'	≡ 1 梯度/100	≈ 0.157 080×10-3 rad
centesimal second of arc	"	≡ 1 梯度/(10 000)	≈ 1.570 796×10-6 rad
degree (of arc)	°	≡ $\frac{1}{360}$圆周 ≡ $\frac{\pi}{180}$rad	≈ 17.453 293×10-3 rad
梯度 (角); gradian; gon	grad	≡ $\frac{1}{400}$圆周 ≡ $\frac{2\pi}{400}$rad ≡ 0.9°	≈ 15.707 963×10-3 rad
八分之一圆		≡ 45°	≈ 0.785 398 rad
象限		≡ 90°	≈ 1.570 796 rad
弧度（SI单位）	rad	The angle subtended at the center of a circle by an arc whose length is equal to the circle's radius. One full revolution encompasses 2π radians.	= 1 rad
六分之一圆		≡ 60°	≈ 1.047 198 rad
sign		≡ 30°	≈ 0.523 599 rad

立体角

立体角

单位名称	符号	定义	与SI的关系
球面度（SI单位）	sr	立体角 subtended at the center of a sphere of radius r by a portion of the surface of the sphere having an area r2. A sphere encompasses 4π sr.	= 1 sr

质量

Notes:

• 查看重量条目以获取关于质量/重量的区别和换算方法。
• Avoirdupois is a system of mass based on a pound of 16 ounces, while Troy weight is the system of mass where 12 troy ounces equals one troy pound.
• In this table, the unit gee is used to denote standard gravity in order to avoid confusion with the "g" symbol for grams.
• 在物理学中，the pound of mass is sometimes written lbm to distinguish it from the pound-force (lbf). It should not be read as the mongrel unit "pound metre".

质量

单位名称	符号	定义	与SI单位的关系
牛股(cowton)	ctn	0.9487t = 1 ctn
atomic mass unit, unified	u; AMU		≈ 1.660 538 73×10−27 ± 1.3×10−36 kg
atomic unit of mass, electron rest mass	me		≈ 9.109 382 15×10−31 ± 45×10−39 kg
bag (coffee)		≡ 60 kg	= 60 kg
bag (Portland cement)		≡ 94 lb av	= 42.637 682 78 kg
barge		≡ $22\frac{1}{2}$sh tn	= 20 411.656 65 kg
carat	kt	≡ $3\frac{1}{6}$gr	≈ 205.196 548 333 mg
carat（公制）	ct	≡ 200 mg	= 200 mg
clove		≡ 8 lb av	= 3.628 738 96 kg
crith			≈ 89.9349 mg
dalton	Da		≈ 1.660 902 10×10−27 ± 1.3×10−36 kg
dram (apothecary; troy)	dr t	≡ 60 gr	= 3.887 9346 g
dram (avoirdupois)	dr av	≡ $22\frac{11}{32}$gr	= 1.771 845 195 3125 g
electronvolt	eV	≡ 1 eV (energy unit) / c2	= 1.7826×10-36 kg
gamma	γ	≡ 1 μg	= 1 μg
grain	gr	≡ $\frac{1}{7000}$lb av	≡ 64.798 91 mg
grave	G	grave 是千克的原名	≡ 1 kg
英担（长）	long cwt or cwt	≡ 112 lb av	= 50.802 345 44 kg
英担（短）、百磅	sh cwt	≡ 100 lb av	= 45.359 237 kg
千克	kg	≡ mass of the prototype near Paris (≈ mass of 1L of water)	≡ 1 kg (SI base unit)
kip	kip	≡ 1000 lb av	= 453.592 37 kg
mark		≡ 8 oz t	= 248.827 8144 g
mite		≡ $\frac{1}{20}$gr	= 3.239 9455 mg
mite（公制）		≡ $\frac{1}{20}$g	= 50 mg
金衡盎司	oz t	≡ $\frac{1}{12}$lb t	= 31.103 4768 g
常衡盎司	oz av	≡ $\frac{1}{16}$lb	= 28.349 523 125 g
盎司 (美国食品标签)	oz	≡ 28 g	= 28 g
英钱	dwt; pwt	≡ $\frac{1}{20}$oz t	= 1.555 173 84 g
point		≡ $\frac{1}{100}$ct	= 2 mg
磅	lb	≡ slug·ft/s2	= 0.45359237 kg
常衡磅	lb av	≡ 0.453 592 37 kg = 7000 grains	≡ 0.453 592 37 kg
公制磅		≡ 500 g	= 500 g
金衡磅	lb t	≡ 5 760 grains	= 0.373 241 7216 kg
quarter（英制）		≡ $\frac{1}{4}$long cwt = 2 st = 28 lb av	= 12.700 586 36 kg
quarter (非正式)		≡ $\frac{1}{4}$short tn	= 226.796 185 kg
quarter, long (非正式)		≡ $\frac{1}{4}$long tn	= 254.011 7272 kg
quintal（公制）	q	≡ 100 kg	= 100 kg
scruple (apothecary)	s ap	≡ 20 gr	= 1.295 9782 g
sheet		≡ $\frac{1}{700}$lb av	= 647.9891 mg
slug; geepound; hyl	slug	≡ 1 gee × 1 lb av × 1 s2/ft	≈ 14.593 903 kg
stone	st	≡ 14 lb av	= 6.350 293 18 kg
ton, assay (long)	AT	≡ 1 mg × 1 long tn ÷ 1 oz t	≈ 32.666 667 g
ton, assay (short)	AT	≡ 1 mg × 1 sh tn ÷ 1 oz t	≈ 29.166 667 g
长吨	long tn or ton	≡ 2 240 lb	= 1 016.046 9088 kg
短吨	sh tn	≡ 2 000 lb	= 907.184 74 kg
tonne (mts unit)	t	≡ 1 000 kg	= 1 000 kg
wey		≡ 252 lb = 18 st	= 114.305 277 24 kg (variants exist)
Zentner	Ztr.	Definitions vary; see and.

密度

密度

单位名称	符号	定义	与SI单位的关系
克每毫升	g/mL	≡ g/mL	= 7003100000000000000♠1000 kg/m3
千克每立方米（SI单位）	kg/m3	≡ kg/m3	= 1 kg/m3
千克每升	kg/L	≡ kg/L	= 7003100000000000000♠1000 kg/m3
盎司 (avoirdupois) 每立方英尺	oz/ft3	≡ oz/ft3	≈ 7000100115396100000♠1.001153961 kg/m3
盎司 (avoirdupois) 每立方英寸	oz/in3	≡ oz/in3	≈ 7003172999404399999♠1.729994044×103 kg/m3
盎司 (avoirdupois) 每加仑（英制）	oz/gal	≡ oz/gal	≈ 7000623602329100000♠6.236023291 kg/m3
盎司 (avoirdupois) 每加仑 (美国容积)	oz/gal	≡ oz/gal	≈ 7000748915170700000♠7.489151707 kg/m3
磅 (avoirdupois) 每立方英尺	lb/ft3	≡ lb/ft3	≈ 7001160184633700000♠16.01846337 kg/m3
磅 (avoirdupois) 每立方英寸	lb/in3	≡ lb/in3	≈ 7004276799047100000♠2.767990471×104 kg/m3
磅 (avoirdupois) 每加仑（英制）	lb/gal	≡ lb/gal	≈ 7001997763726600000♠99.77637266 kg/m3
磅 (avoirdupois) 每加仑（美国容积）	lb/gal	≡ lb/gal	≈ 7002119826427300000♠119.8264273 kg/m3
slug per cubic foot	slug/ft3	≡ slug/ft3	≈ 7002515378818400000♠515.3788184 kg/m3

时间

时间

单位名称	符号	定义	与SI单位的关系
atomic unit of time	au	≡ a0/(α·c)	≈ 2.418 884 254×10−17 s
蔀		≡指回归年与朔望月与太阳日的最短循环 = 76年	= 2.398 3776×109 s
世纪	c	≡ 100 a (参见下方年的长度定义)	= 100 年
日（天）	d	= 24 h	= 1440 min = 86400 s
恒星日	d	≡ 是地球上某点对某个恒星连续两次经过其上中天的时间间隔 (国际天球参考框架)	≈ 86 164.1 s
年代	dec	≡ 10 a (see below for definition of year length)	= 10 年
fortnight	fn	≡ 2 周	= 1 209 600 s
helek (希伯来历)		≡ $\frac{1}{1080}$h	= 3.3 s
Hipparchic cycle		≡ 4 Callippic cycles - 1 d	= 9.593 424×109 s
小时	h	≡ 60 min	= 3 600 s
jiffy	j	≡ $\frac{1}{60}$s	= .016 s
jiffy (alternate)	ja	≡ $\frac{1}{100}$s	= 10 ms
刻（钟）（四分之一小时）		≡ $\frac{1}{4}$h = $\frac{1}{96}$d	= $60 \times \frac{60}{4}$s=900 s=$\frac{60}{4}$min=15 min
刻（钟）（旧制） (traditional)		≡ $\frac{1}{100}$d	= $24 \times 60 \times \frac{60}{100}$s = 864 s = $24 \times \frac{60}{100}$min = 14.4 min
lustre; lustrum		≡ 5 a of 365 d	= 1.5768×108 s
章 (历法);		≡ 110 mo (hollow) + 125 mo (full) = 6940 d ≈ 19 a	= 5.996 16×108 s
千年		≡ 1 000 a (see below for definition of year length)	= 1000 年
beat	md	≡ $\frac{1}{1000}$d	= $24 \times 60 \times \frac{60}{1000}$s = 86.4 s
分钟	min	≡ 60 s, due to leap seconds sometimes 59 s or 61 s,	= 60 s
moment		≡ 90 s	= 90 s
月 (full)	mo	≡ 30 d	= 2 592 000 s
月 (Greg. av.)	mo	Average Gregorian month = 1 a (Gregorian average) / 12 = 365.242 5 d / 12 = 30.436 875 d	≈ 2.6297×106 s
月 (hollow)	mo	≡ 29 d	= 2 505 600 s
朔望月	mo	Cycle time of moon phases ≈ 29.530 589 d (Average)	≈ 2.551×106 s
octaeteris		= 48 mo (full) + 48 mo (hollow) + 3 mo (full)= 8 a of 365.25 d = 2922 d	= 2.524 608×108 s
Planck time		≡ (Gℏ/c5)½	≈ 1.351 211 868×10−43 s
秒	s	铯133原子基态的两个超精细能阶间跃迁对应辐射的9,192,631,770个周期的持续时间(but other seconds are sometimes used in astronomy)	(SI base unit)
shake		≡ 10−8 s	= 10 ns
sigma		≡ 10−6 s	= 1 μs
Sothic cycle		≡ 1 461 a of 365 d	= 4.607 4096×1010 s
svedberg	S	≡ 10−13 s	= 100 fs
周	wk	≡ 7 d	= 168 h = 10 080 min = 604 800 s
年（公历）	a, y, or yr	= 365.2425 d average, calculated from common years (365 d) plus leap years (366 d) on most years divisible by 4. See leap year for details.	= 31 556 952 s
年（儒略历）	a, y, or yr	= 365.25 d average, calculated from common years (365 d) plus one leap year (366 d) every four years	= 31 557 600 s
恒星年	a, y, or yr	≡ time taken for Sun to return to the same position with respect to the stars of the celestial sphere	≈ 365.256 363 d ≈ 31 558 149.7632 s
回归年	a, y, or yr	≡ Length of time it takes for the Sun to return to the same position in the cycle of seasons	≈ 365.242 190 d ≈ 31 556 925 s
旬		= 10 d
Where UTC is observed, the length of time units longer than 1 s may increase or decrease by 1 s if a leap second occurs during the time interval of interest.

频率

频率

单位名称	符号	定义	与SI单位的关系
hertz (SI unit)	Hz	≡ Number of cycles per second	= 1 Hz = 1/s
每分钟转数	rpm	≡ One unit rpm equals one rotation completed around a fixed axis in one minute of time.	≈

速度或速率

速度

单位名称	符号	定义	与SI单位的关系
英尺每小时	fph	≡ 1 ft/h	≈ 8.466 667×10−5 m/s
英尺每分钟	fpm	≡ 1 ft/min	= 5.08×10−3 m/s
英尺每秒	fps	≡ 1 ft/s	= 3.048×10−1 m/s
furlong per fortnight		≡ furlong/fortnight	≈ 1.663 095×10−4 m/s
英寸每小时	iph	≡ 1 in/hr	≈ 7.05 556×10−6 m/s
英寸每分钟	ipm	≡ 1 in/min	≈ 4.23 333×10−4 m/s
英寸每秒	ips	≡ 1 in/s	= 2.54×10−2 m/s
千米每小时	km/h	≡ 1 km/h	= $\frac{1}{3.6}$ m/s ≈ 2.777 778×10−1 m/s
节	kn, kt	≡ 1 NM/h = 1.852 km/h	≈ 0.514 444 m/s
节 (Admiralty)	kn	≡ 1 NM (Adm)/h = 1.853 184 km/h	= 0.514 773 m/s
马赫	M	Ratio of the speed to the speed of sound in the medium. Varies especially with temperature. About 1225 km/h (761 mph) in air at sea level to about 1062 km/h (660 mph) at jet altitudes (12,200米（40,000英尺）).Unitless	≈ 340 to 295 m/s for aircraft
metre per second (SI unit)	m/s	≡ 1 m/s	= 1 m/s
英里每小时	mph	≡ 1 mi/h	= 0.447 04 m/s
英里每分钟	mpm	≡ 1 mi/min	= 26.8224 m/s
英里每秒	mps	≡ 1 mi/s	= 1 609.344 m/s
真空光速	c	≡ 299 792 458 m/s	= 299 792 458 m/s
空气音速	s	Varies especially with temperature. About 1225 km/h (761 mph) in air at sea level to about 1062 km/h (660 mph) at jet altitudes.	≈ 340 to 295 m/s at aircraft altitudes

A velocity consists of a speed combined with a direction; the speed part of the velocity takes units of speed.

流量（容积）

流量

单位名称	符号	定义	与SI单位的关系
立方英尺每分钟	CFM	≡ 1 ft3/min	= 6996471947443200000♠4.719474432×10−4 m3/s
立方英尺每秒	ft3/s	≡ 1 ft3/s	= 6998283168465920000♠0.028316846592 m3/s
立方英寸每分钟	in3/min	≡ 1 in3/min	= 7000273117700000000♠2.7311773×10-7 m3/s
立方英寸每秒	in3/s	≡ 1 in3/s	= 6995163870640000000♠1.6387064×10−5 m3/s
立方米每秒（SI单位）	m3/s	≡ 1 m3/s	= 1 m3/s
加仑（美国容积）每日	GPD	≡ 1 gal/d	= 7000438126363000000♠4.381263638×10-8 m3/s
加仑（美国容积）每小时	GPH	≡ 1 gal/h	= 7000105150327000000♠1.051503273×10-6 m3/s
加仑（美国容积）每分钟	GPM	≡ 1 gal/min	= 6995630901964000000♠6.30901964×10−5 m3/s
升每分钟	LPM	≡ 1 L/min	= 1.6×10-5 m3/s

加速度

加速度

Name of unit	Symbol	Definition	Relation to SI units
foot per hour per second	fph/s	≡ 1 ft/(h·s)	≈ 8.466 667×10−5 m/s2
foot per minute per second	fpm/s	≡ 1 ft/(min·s)	= 5.08×10−3 m/s2
英尺每二次方秒	fps2	≡ 1 ft/s2	= 3.048×10−1 m/s2
gal; galileo	Gal	≡ 1 cm/s2	= 10−2 m/s2
inch per minute per second	ipm/s	≡ 1 in/(min·s)	≈ 4.233 333×10−4 m/s2
英寸每二次方秒	ips2	≡ 1 in/s2	= 2.54×10−2 m/s2
knot per second	kn/s	≡ 1 kn/s	≈ 5.144 444×10−1 m/s2
米每二次方秒 (SI)	m/s2	≡ 1 m/s2	= 1 m/s2
mile per hour per second	mph/s	≡ 1 mi/(h·s)	= 4.4704×10−1 m/s2
mile per minute per second	mpm/s	≡ 1 mi/(min·s)	= 26.8224 m/s2
英里每二次方秒	mps2	≡ 1 mi/s2	= 1.609 344×103 m/s2
standard gravity	g	≡ 9.806 65 m/s2	= 9.806 65 m/s2

力

力

Name of unit	Symbol	Definition	Relation to SI units
atomic unit of force		≡ me·α2·c2/a0	≈ 8.238 722 06×10−8 N
达因 (cgs unit)	dyn	≡ g·cm/s2	= 10−5 N
kilogram-force; kilopond; grave-force	kgf; kp; Gf	≡ $g \times 1$kg	= 9.806 65 N
kip; kip-force	kip; kipf; klbf	≡ $g \times 1000$lb	= 4.448 221 615 2605×103 N
milligrave-force, gravet-force	mGf; gf	≡ 'g' × 1 g	= 9.806 65 mN
牛顿 (单位)（SI单位）	N	A force capable of giving a mass of one kg an acceleration of one metre per second, per second.	= 1 N = 1 kg·m/s2
ounce-force	ozf	≡ $g \times 1$oz	= 0.278 013 850 953 7812 N
pound-force	lbf	≡ $g \times 1$lb	= 4.448 221 615 2605 N
poundal	pdl	≡ 1 lb·ft/s2	= 0.138 254 954 376 N
sthene (mts unit)	sn	≡ 1 t·m/s2	= 1×103 N
ton-force	tnf	≡ $g \times 1$sh tn	= 8.896 443 230 521×103 N

See also: Conversion between weight (force) and mass

压力或机械应力Pressure or mechanical stress

Pressure

Name of unit单位名称	Symbol符号	Definition定义	Relation to SI units与SI单位的换算
标准大气压	atm		≡ 101 325 Pa
工程大气压	at	≡ 1 kgf/cm2	= 9.806 65×104 Pa
巴	bar		≡ 105 Pa
毫巴	mbar	= 10−3 Bar
barye (cgs unit)		≡ 1 dyn/cm2	= 0.1 Pa
厘米汞柱 (4 °C /39.2 °F)	cmHg	≡ 13 595.1 kg/m3 × 1 cm × g	≈ 1.333 22×103 Pa
厘米水柱 (4 °C /39.2 °F)	cmH2O	≈ 999.972 kg/m3 × 1 cm × g	≈ 98.063 8 Pa
英尺汞柱 (4 °C /39.2 °F)	ftHg	≡ 13 595.1 kg/m3 × 1 ft × g	≈ 40.636 66×103 Pa
英尺水柱 (4 °C /39.2 °F)	ftH2O	≈ 999.972 kg/m3 × 1 ft × g	≈ 2.988 98×103 Pa
英寸汞柱 (4 °C /39.2 °F)	inHg	≡ 13 595.1 kg/m3 × 1 in × g	≈ 3.386 389×103 Pa
英寸水柱 (4 °C /39.2 °F)	inH2O	≈ 999.972 kg/m3 × 1 in × g	≈ 249.082 Pa
公斤力每平方毫米	kgf/mm2	≡ 1 kgf/mm2	= 9.806 65×106 Pa
kip per square inch	ksi	≡ 1 kipf/sq in	≈ 6.894 757×106 Pa
微米汞柱 (4 °C /39.2 °F)	$\mu$mHg	≡ 13 595.1 kg/m3 × 1 $\mu$m × g ≈ 0.001 torr	≈ 0.133 322 4 Pa
毫米汞柱 (4 °C /39.2 °F)	mmHg	≡ 13 595.1 kg/m3 × 1 mm × g ≈ 1 torr	≈ 133.3224 Pa
毫米水柱 (4 °C /39.2 °F)	mmH2O	≈ 999.972 kg/m3 × 1 mm × g = 0.999 972 kgf/m2	= 9.806 38 Pa
帕斯卡 (SI unit)	Pa	≡ N/m2 = kg/(m·s2)	= 1 Pa
pièze (mts unit)	pz	≡ 1 000 kg/m·s2	= 1×103 Pa = 1 kPa
磅力每平方英尺	psf	≡ 1 lbf/ft2	≈ 47.880 26 Pa
磅力每平方英寸	psi	≡ 1 lbf/in2	≈ 6.894 757×103 Pa
poundal per square foot	pdl/sq ft	≡ 1 pdl/sq ft	≈ 1.488 164 Pa
short ton per square foot		≡ 1 sh tn $\times\frac{g}{1}$sq ft	≈ 95.760 518×103 Pa
托	torr	≡ $101 \frac{325}{760}$Pa	≈ 133.322 4 Pa

Torque or moment of force

Torque

单位名称	符号	定义	与SI单位的关系
foot-pound force	ft lbf	≡ $g \times 1$lb × 1 ft	= 1.355 817 948 331 4004 N·m
foot-poundal	ft pdl	≡ 1 lb·ft2/s2	= 4.214 011 009 380 48×10−2 N·m
inch-pound force	in lbf	≡ $g \times 1$lb × 1 in	= 0.112 984 829 027 6167 N·m
米·千克	m kg	≡ N × m / g	≈ 0.101 971 621 N·m
牛·米（SI单位）	N·m	≡ N × m = kg·m2/s2	= 1 N·m

能量

能量

单位名称	符号	定义	与SI单位的关系
barrel of oil equivalent	bboe	≈ 5.8×106 BTU59 °F	≈ 6.12×109 J
British thermal unit (ISO)	BTUISO	≡ 1.0545×103 J	= 1.0545×103 J
British thermal unit (International Table)	BTUIT		= 1.055 055 852 62×103 J
British thermal unit (mean)	BTUmean		≈ 1.055 87×103 J
British thermal unit (thermochemical)	BTUth		≈ 1.054 350×103 J
British thermal unit (39 °F)	BTU39 °F		≈ 1.059 67×103 J
British thermal unit (59 °F)	BTU59 °F	≡ 1.054 804×103 J	= 1.054 804×103 J
British thermal unit (60 °F)	BTU60 °F		≈ 1.054 68×103 J
British thermal unit (63 °F)	BTU63 °F		≈ 1.0546×103 J
calorie (International Table)	calIT	≡ 4.1868 J	= 4.1868 J
calorie (mean)	calmean	1⁄100 of the energy required to warm one gram of air-free water from 0 °C to 100 °C @ 1 atm	≈ 4.190 02 J
calorie (thermochemical)	calth	≡ 4.184 J	= 4.184 J
卡路里 (3.98 °C)	cal3.98 °C		≈ 4.2045 J
卡路里 (15 °C)	cal15 °C	≡ 4.1855 J	= 4.1855 J
卡路里 (20 °C)	cal20 °C		≈ 4.1819 J
摄氏度 heat unit (International Table)	CHUIT	≡ 1 BTUIT × 1 K/°R	= 1.899 100 534 716×103 J
cubic centimetre of atmosphere; standard cubic centimetre	cc atm; scc	≡ 1 atm × 1 cm3	= 0.101 325 J
cubic foot of atmosphere; standard cubic foot	cu ft atm; scf	≡ 1 atm × 1 ft3	= 2.869 204 480 9344×103 J
cubic foot of natural gas		≡ 1 000 BTUIT	= 1.055 055 852 62×106 J
cubic yard of atmosphere; standard cubic yard	cu yd atm; scy	≡ 1 atm × 1 yd3	= 77.468 520 985 2288×103 J
electronvolt	eV	≡ e × 1 V	≈ 1.602 177 33×10−19 ± 4.9×10-26 J
erg (cgs unit)	erg	≡ 1 g·cm2/s2	= 10−7 J
foot-pound force	ft lbf	≡ g × 1 lb × 1 ft	= 1.355 817 948 331 4004 J
foot-poundal	ft pdl	≡ 1 lb·ft2/s2	= 4.214 011 009 380 48×10−2 J
gallon-atmosphere（英制）	imp gal atm	≡ 1 atm × 1 gal (imp)	= 460.632 569 25 J
gallon-atmosphere（美国）	US gal atm	≡ 1 atm × 1 gal（美国）	= 383.556 849 0138 J
hartree, atomic unit of energy	Eh	≡ me·α2·c2 (= 2 Ry)	≈ 4.359 744×10−18 J
horsepower-hour	hp·h	≡ 1 hp × 1 h	= 2.684 519 537 696 172 792×106 J
inch-pound force	in lbf	≡ g × 1 lb × 1 in	= 0.112 984 829 027 6167 J
joule (SI unit)	J	The work done when a force of one newton moves the point of its application a distance of one metre in the direction of the force.	= 1 J = 1 m·N = 1 kg·m2/s2 = 1 C·V = 1 W·s
千卡、大卡	kcal; Cal	≡ 1 000 calIT	= 4.1868×103 J
kilowatt-hour; Board of Trade Unit	kW·h; B.O.T.U.	≡ 1 kW × 1 h	= 3.6×106 J
litre-atmosphere	l atm; sl	≡ 1 atm × 1 L	= 101.325 J
quad		≡ 1015 BTUIT	= 1.055 055 852 62×1018 J
rydberg	Ry	≡ R∞·ℎ·c	≈ 2.179 872×10−18 J
therm (E.C.)		≡ 100 000 BTUIT	= 105.505 585 262×106 J
therm（美国）		≡ 100 000 BTU59 °F	= 105.4804×106 J
thermie	th	≡ 1 McalIT	= 4.1868×106 J
ton of coal equivalent	TCE	≡ 7 Gcalth	= 29.3076×109 J
ton of oil equivalent	TOE	≡ 10 Gcalth	= 41.868×109 J
ton of TNT	tTNT	≡ 1 Gcalth	= 4.184×109 J

Power or heat flow rate

Power

单位名称	符号	定义	与SI单位的关系
atmosphere-cubic centimetre per minute	atm ccm	≡ 1 atm × 1 cm3/min	= 1.688 75×10−3 W
atmosphere-cubic centimetre per second	atm ccs	≡ 1 atm × 1 cm3/s	= 0.101 325 W
atmosphere-cubic foot per hour	atm cfh	≡ 1 atm × 1 cu ft/h	= 0.797 001 244 704 W
atmosphere-cubic foot per minute	atm·cfm	≡ 1 atm × 1 cu ft/min	= 47.820 074 682 24 W
atmosphere-cubic foot per second	atm cfs	≡ 1 atm × 1 cu ft/s	= 2.869 204 480 9344×103 W
BTU (International Table) per hour	BTUIT/h	≡ 1 BTUIT/h	≈ 0.293 071 W
BTU (International Table) per minute	BTUIT/min	≡ 1 BTUIT/min	≈ 17.584 264 W
BTU (International Table) per second	BTUIT/s	≡ 1 BTUIT/s	= 1.055 055 852 62×103 W
calorie (International Table) per second	calIT/s	≡ 1 calIT/s	= 4.1868 W
erg per second	erg/s	≡ 1 erg/s	= 10−7 W
foot-pound-force per hour	ft lbf/h	≡ 1 ft lbf/h	≈ 3.766 161×10−4 W
foot-pound-force per minute	ft lbf/min	≡ 1 ft lbf/min	= 2.259 696 580 552 334×10−2 W
foot-pound-force per second	ft lbf/s	≡ 1 ft lbf/s	= 1.355 817 948 331 4004 W
horsepower (boiler)	bhp	≈ 34.5 lb/h × 970.3 BTUIT/lb	≈ 9.810 657×103 W
horsepower (European electrical)	hp	≡ 75 kp·m/s	= 736 W
horsepower (imperial electrical)	hp	≡ 746 W	= 746 W
horsepower (imperial mechanical)	hp	≡ 550 ft lbf/s	= 745.699 871 582 270 22 W
horsepower（公制）	hp	≡ 75 m kgf/s	= 735.498 75 W
litre-atmosphere per minute	L·atm/min	≡ 1 atm × 1 L/min	= 1.688 75 W
litre-atmosphere per second	L·atm/s	≡ 1 atm × 1 L/s	= 101.325 W
lusec	lusec	≡ 1 L·µmHg/s	≈ 1.333×10−4 W
poncelet	p	≡ 100 m kgf/s	= 980.665 W
square foot equivalent direct radiation	sq ft EDR	≡ 240 BTUIT/h	≈ 70.337 057 W
ton of air conditioning		≡ 2000 lbs of ice melted / 24 h	≈ 3 504 W
ton of refrigeration（英制）		≡ 2240 lb × iceIT / 24 h: iceIT = 144 °F × 2326 J/kg.°F	≈ 3.938 875×103 W
ton of refrigeration (IT)		≡ 200 lbs × iceIT / 24 h: iceIT = 144° × 2326 J/kg.°F	≈ 3.516 853×103 W
watt (SI unit)	W	The power which in one second of time gives rise to one joule of energy.	= 1 W = 1 J/s = 1 N·m/s = 1 kg·m2/s3

Action

Action

Name of unit	Symbol	Definition	Relation to SI units
atomic unit of action	au	≡ ℏ ≡ ℎ/2π	≈ 1.054 571 68×10−34 J·s

Dynamic 黏度

Dynamic 黏度

单位名称	符号	定义	与SI单位的关系
pascal second (SI unit)	Pa·s	≡ N·s/m2, kg/(m·s)	= 1 Pa·s
poise (cgs unit)	P	≡ 1 barye·s	= 0.1 Pa·s
pound per foot hour	lb/(ft·h)	≡ 1 lb/(ft·h)	≈ 4.133 789×10-4 Pa·s
pound per foot second	lb/(ft·s)	≡ 1 lb/(ft·s)	≈ 7000148816400000000♠1.488164 Pa·s
pound-force second per square foot	lbf·s/ft2	≡ 1 lbf·s/ft2	≈ 7001478802600000000♠47.88026 Pa·s
pound-force second per square inch	lbf·s/in2	≡ 1 lbf·s/in2	≈ 7003689475700000000♠6894.757 Pa·s

Kinematic 黏度

Kinematic 黏度

单位名称	符号	定义	与SI单位的关系
square foot per second	ft2/s	≡ 1 ft2/s	= 6998929030400000000♠0.09290304 m2/s
square metre per second (SI unit)	m2/s	≡ 1 m2/s	= 1 m2/s
stokes (cgs unit)	St	≡ 10−4 m2/s	= 10−4 m2/s

电流

电流

单位名称	符号	定义	与SI单位的关系
ampere (SI base unit)	A	≡ The constant current needed to produce a force of 2 ×10-7 newton per metre between two straight parallel conductors of infinite length and negligible circular cross-section placed one metre apart in a vacuum.	= 1 A
electromagnetic unit; abampere (cgs unit)	abamp	≡ 10 A	= 10 A
esu per second; statampere (cgs unit)	esu/s	≡ (0.1 A·m/s) / c	≈ 6990333564100000000♠3.335641×10−10 A

Electric charge

Electric charge

Name of unit	Symbol	Definition	Relation to SI units
abcoulomb; electromagnetic unit (cgs unit)	abC; emu	≡ 10 C	= 10 C
atomic unit of charge	au	≡ e	≈ 1.602 176 462×10−19 C
coulomb (SI unit)	C	≡ The amount of electricity carried in one second of time by one ampere of current.	= 1 C = 1 A·s
faraday	F	≡ 1 mol × NA·e	≈ 96 485.3383 C
statcoulomb; franklin; electrostatic unit (cgs unit)	statC; Fr; esu	≡ (0.1 A·m) / c	≈ 3.335 641×10−10 C

Electric dipole

Electric dipole

Name of unit	Symbol	Definition	Relation to SI units
atomic unit of electric dipole moment	ea0		≈ 8.478 352 81×10-30 C·m
coulomb meter	C·m		= 1 C · 1 m
debye	D	= 10−10 esu·Å	= 3.33564095×10-30 C·m

Electromotive force, electric potential difference

Voltage, electromotive force

Name of unit	符号	Definition	Relation to SI units
abvolt (cgs unit)	abV	≡ 1×10-8 V	= 1×10-8 V
statvolt (cgs unit)	statV	≡ c· (1 μJ/A·m)	= 299.792 458 V
伏特 (SI unit)	V	The difference in electric potential across two points along a conducting wire carrying one ampere of constant current when the power dissipated between the points equals one watt.	= 1 V = 1 W/A = 1 kg·m2/(A·s3)

Electrical resistance

Electrical resistance

Name of unit	Symbol	Definition	Relation to SI units
ohm (SI unit)	Ω	The resistance between two points in a conductor when one volt of electric potential difference, applied to these points, produces one ampere of current in the conductor.	= 1 Ω = 1 V/A = 1 kg·m2/(A2·s3)

电容Capacitance

Capacitor's ability to store charge

Name of unit	Symbol	Definition	Relation to SI units
farad (SI unit)	F	The capacitance between two parallel plates that results in one volt of potential difference when charged by one coulomb of electricity.	= 1 F = 1 C/V = 1 A2·s4/(kg·m2)

Magnetic flux

magnetic flux

Name of unit	Symbol	Definition	Relation to SI units
maxwell (CGS unit)	Mx	≡ 10−8 Wb	= 1×10-8 Wb
weber (SI unit)	Wb	Magnetic flux which, linking a circuit of one turn, would produce in it an electromotive force of 1 volt if it were reduced to zero at a uniform rate in 1 second.	= 1 Wb = 1 V·s = 1 kg·m2/(A·s2)

Magnetic flux density

What physicists call Magnetic field is called Magnetic flux density by electrical engineers and magnetic induction by applied mathematicians and electrical engineers.

Name of unit	Symbol	Definition	Relation to SI units
gauss (CGS unit)	G	≡ Mx/cm2 = 10−4 T	= 1×10-4 T
tesla (SI unit)	T	≡ Wb/m2	= 1 T = 1 Wb/m2 = 1 kg/(A·s2)

Inductance

Inductance

Name of unit	Symbol	Definition	Relation to SI units
henry (SI unit)	H	The inductance of a closed circuit that produces one volt of electromotive force when the current in the circuit varies at a uniform rate of one ampere per second.	= 1 H = 1 Wb/A = 1 kg·m2/(A·s)2

温度

更多信息：Conversion of units of temperature

温度

单位名称	符号	定义	与SI单位的关系
摄氏温标 Celsius	°C	°C ≡ K $-273.15$	[K] ≡ [°C] $+273.15$
degree Delisle	°De		[K] = 373.15 − [°De] $\times \frac{2}{3}$
华氏温标 Fahrenheit	°F	°F ≡ °C $\times\frac{9}{5}+32$	[K] ≡ ([°F] + 459.67) $\times\frac{9}{5}$
牛顿温标 Newton	°N		[K] = [°N] $\times \frac{100}{33}+273.15$
兰金温标 Rankine	°R;	°R ≡ K $\times\frac{9}{5}$	[K] ≡ [°R] $\times\frac{5}{9}$
列氏温标 Réaumur	°Ré		[K] = [°Ré] $\times\frac{5}{4}+273.15$
罗氏温标 Rømer	°Rø		[K] = ([°Rø] − 7.5) $\times\frac{40}{21}+273.15$
Regulo Gas Mark	GM;	°F ≡ GM $\times 25+300$	[K] ≡ [GM] $\times \frac{125}{9}+422.038$
开氏温标 Kelvin(国际标准单位)	K	≡ 1/273.16 of the thermodynamic temperature of the triple point of water.	≡ 1 K

Information entropy

Information entropy

Name of unit	Symbol	Definition	Relation to SI units	Relation to bits
SI unit	J/K	≡ J/K	= 1 J/K
nat; nip; nepit	nat	≡ kB	= 1.380 650 5(23)×10-23 J/K
bit; shannon	bit; b; Sh	≡ ln(2) × kB	= 9.569 940 (16)×10-24 J/K	= 1 bit
ban; hartley	ban; Hart	≡ ln(10) × kB	= 3.179 065 3(53)×10-23 J/K
nibble		≡ 4 bits	= 3.827 976 0(64)×10-23 J/K	= 22 bit
byte	B	≡ 8 bits	= 7.655 952 (13)×10-23 J/K	= 23 bit
千字节（十进制）	kB	≡ 1 000 B	= 7.655 952 (13)×10-20 J/K	= 8×103 bit = 8000 bit
kibibyte	KB; KiB	≡ 1 024 B	= 7.839 695 (13)×10-20 J/K	= 213 bit = 8192 bit

Often, information entropy is measured in shannons, whereas the (discrete) storage space of digital devices is measured in bits. Thus, uncompressed redundant data occupy more than one bit of storage per shannon of information entropy. The multiples of a bit listed above are usually used with this meaning. Other times the bit is used as a measure of information entropy and is thus a synonym of shannon.

Luminous intensity

The candela is the preferred nomenclature for the SI unit.

Luminous intensity

Name of unit	Symbol	Definition	Relation to SI units
candela (SI base unit); candle	cd	The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.	= 1 cd
candlepower (new)	cp	≡ cd The use of candlepower as a unit is discouraged due to its ambiguity.	= 1 cd
candlepower (old, pre-1948)	cp	Varies and is poorly reproducible.Approximately 0.981 cd.	≈ 0.981 cd

Luminance

Luminance

Name of unit	Symbol	Definition	Relation to SI units
candela per square foot	cd/ft2	≡ cd/ft2	≈ 7001107639104170000♠10.763910417 cd/m2
candela per square inch	cd/in2	≡ cd/in2	≈ 7003155000310000000♠1550.0031 cd/m2
candela per square metre (SI unit); nit (deprecated)	cd/m2	≡ cd/m2	= 1 cd/m2
footlambert	fL	≡ (1/π) cd/ft2	≈ 7000342625909960000♠3.4262590996 cd/m2
lambert	L	≡ (104/π) cd/m2	≈ 7003318309886180000♠3183.0988618 cd/m2
stilb (CGS unit)	sb	≡ 104 cd/m2	≈ 1×104 cd/m2

Luminous flux

Luminous flux

Name of unit	Symbol	Definition	Relation to SI units
lumen (SI unit)	lm	≡ cd·sr	= 1 lm = 1 cd·sr

Illuminance

Illuminance

Name of unit	Symbol	Definition	Relation to SI units
footcandle; lumen per square foot	fc	≡ lm/ft2	= 7001107639104170000♠10.763910417 lx
lumen per square inch	lm/in2	≡ lm/in2	≈ 7003155000310000000♠1550.0031 lx
lux (SI unit)	lx	≡ lm/m2	= 1 lx = 1 lm/m2
phot (CGS unit)	ph	≡ lm/cm2	= 1×104 lx

Radiation - source activity

Radioactivity

Name of unit	Symbol	Definition	Relation to SI units
becquerel (SI unit)	Bq	≡ Number of disintegrations per second	= 1 Bq = 1/s
curie	Ci	≡ 3.7×1010 Bq	= 3.7×1010 Bq
rutherford（H）	rd	≡ 1 MBq	= 1×106 Bq

Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (s⁻¹), Hz is used only for periodic phenomena, and Bq is only used for stochastic processes associated with radioactivity.

Radiation - exposure

Radiation - exposure

Name of unit	Symbol	Definition	Relation to SI units
roentgen	R	1 R ≡ 2.58×10-4 C/kg	= 2.58×10-4 C/kg

The roentgen is not an SI unit and the NIST strongly discourages its continued use.

Radiation - absorbed dose

Radiation - absorbed dose

Name of unit	Symbol	Definition	Relation to SI units
gray (SI unit)	Gy	≡ 1 J/kg = 1 m2/s2	= 1 Gy
rad	rad	≡ 0.01 Gy	= 0.01 Gy

Radiation - equivalent dose

Radiation - equivalent dose

Name of unit	Symbol	Definition	Relation to SI units
Röntgen equivalent man	rem	≡ 0.01 Sv	= 0.01 Sv
sievert (SI unit)	Sv	≡ 1 J/kg	= 1 Sv

Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantities, this is not the case. The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on many factors, thus a new unit was needed to denote the biological effectiveness of that dose on the body; this is known as the equivalent dose and is shown in Sv. The general relationship between absorbed dose and equivalent dose can be represented as

H = Q · D

where H is the equivalent dose, D is the absorbed dose, and Q is a dimensionless quality factor. Thus, for any quantity of D measured in Gy, the numerical value for H measured in Sv may be different.

Software tools

Home and office computers come with converters in bundled spreadsheet applications or can access free converters via the Internet. Units and measurements can be easily converted using these tools, but only if the units are explicitly defined and the conversion is compatible (e.g., cmHg to kPa).

General commercial sources of converters

• Advanced electronic calculators have unit-conversion functionality.
• Spreadsheet programs usually provide conversion functions or formulas or the user can write their own.
• Commercial mathematical, scientific and technical applications often include converters.

In fiction

When a measure is converted to another unit in a fiction work like a novel or film, the value often loses meaning (as in numerology) or gets too many significant digits ("40 miles" turns into "64 km"). For this reason, authors sometimes choose numbers that can be converted easily. Most notably, distances measured in miles often begin with 3 or 5, so the value ghjcfugffyhfdfgjvcgconverted to km also has one significant digit (5 or 8).

参见

• 准确与精密
• 温度单位换算
• 假精确
• 英制单位
• 国际单位制
• 米制

• 自然单位制
• 数值修约规则
• 有效数字
• 国际单位制词头
• 计量单位

参考资料

Notes

外部链接

• Statutory Instrument 1995 No. 1804 Units of measurement regulations 1995 From legislation.gov.uk
• How Many? A dictionary of units of measurement
• NIST: Fundamental physical constants — Non-SI unitsPDF (35.7 KB)
• NIST Guide to SI Units Many conversion factors listed.
• The Unified Code for Units of Measure
• Units, Symbols, and Conversions XML Dictionary
• Unit converter online （英文）
• 开放式目录计划中和Units of Measurement Software相关的内容
• 开放式目录计划中和Units of Measurement Online Conversion相关的内容