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SI units

Source:
The New Oxford Dictionary for Scientific Writers and Editors

Appendix 7 SI units

Table 7.1 Base and dimensionless SI units

Physical quantity

Name of SI unit

Symbol for SI unit

length

metre

m

mass

kilogram

kg

time

second

s

electric current

ampere

A

thermodynamic temperature

Kelvin

K

luminous intensity

candela

cd

amount of substance

mole

mol

*plane angle

radian

rad

*solid angle

steradian

sr

*dimensionless units

Table 7.2 Decimal multiples and submultiples to be used with SI units

Submultiple

Prefix

Symbol

Multiple

Prefix

Symbol

10−1

deci

d

10

deca

da

10−2

centi

c

102

hector

h

10−3

milli

m

103

kilo

k

10−6

micro

μ

106

mega

M

10−9

nano

n

109

giga

G

10−12

pico

p

1012

tera

T

10−15

femto

f

1015

peta

P

10−18

atto

a

1018

exa

E

10−21

zepto

z

1021

zeta

Z

10−24

yocto

y

1024

yotta

Y

Table 7.3 Derived SI units with special names

Physical quantity

Name of SI unit

Symbol for SI unit

frequency

hertz

Hz

energy

joule

J

force

newton

N

power

watt

W

pressure

pascal

Pa

electric charge

coulomb

C

electric potential difference

volt

V

electric resistance

ohm

Ω

electric conductance

siemens

S

electric capacitance

farad

F

magnetic flux

weber

Wb

inductance

henry

H

magnetic flux density (magnetic induction)

tesla

T

luminous flux

lumen

lm

illuminance

lux

lx

absorbed dose

gray

Gy

activity

becquerel

Bq

dose equivalent

sievert

Sv

Table 7.4 Conversion of units from and to SI units

Length

From

To

m

cm

in

ft

yd

1 metre

1

100

39.3701

3.28084

1.093 61

1 centimetre

0.01

1

0.393 701

0.032 808 4

0.010 936 1

1 inch

0.0254

2.54

1

0.083 333 3

0.027 777 8

1 foot

0.3048

30.48

12

1

0.333 333

1 yard

0.9144

91.44

36

3

1

From

To

km

mi

nmile

1 kilometre

1

0.621 371

0.539 957

1 mile

1.609 34

1

0.868 976

1 nautical mile

1.852 00

1.150 78

1

Area

From

To

m2

cm2

in2

ft2

1 square metre

1

104

1550

10.7639

1 square centimetre

10−4

1

0.155 × 10−3

1.076 39

1 square inch

6.4516 × 10−4

6.4516

1

6.94444 × 10−3

1 square foot

9.2903 × 10−2

929.03

144

1

From

To

m2

km2

yd2

mi2

acre

1 square metre

1

10−6

1.19599

3.86019 × 10−7

2.47 105 × 10−4

1 square kilometre

106

1

1.19599 × 106

0.386019

247.105

1 square yard

0.836 127

8.361 27 × 10−7

1

3.22831 × 10−7

2.066 12 × 10−4

1 square mile

2.589 99 × 106

2.589 99

3.0976 × 106

1

640

1 acre

4.046 86 × 103

4.046 86 × 10−3

4840

1.5625 × 10−3

1

Volume

From

To

m3

cm3

in3

ft3

gallons

1 cubic metre

1

106

6.102 36 × 104

35.3146

219.969

1 cubic centimetre

10−6

1

0.0610236

3.53146 × 10−5

2.199 69 × 10−4

1 cubic inch

1.638 71 × 10−5

16.3871

1

5.78704 × 10−4

3.604 64 × 10−3

1 cubic foot

0.0283168

28316.8

1728

1

6.22882

1 gallon (UK)

4.54609 × 10−3

4546.09

277.42

0.160544

1

Mass

From

To

kg

g

lb

1 kilogram

1

1000

2.204 62

1 gram

10−3

1

2.204 62 × 10−3

1 pound

0.453 592

453.592

1

Energy and work

From

To

J

calIT

kWh

BtuIT

1 joule

1

0.238 846

2.777 78 × 10−7

9.478 13 × 10−4

1 calorie (IT)

4.1868

1

1.16300 × 10−6

3.968 31 × 10−3

1 kilowatt hour

3.6 × 106

8.598 45 × 105

1

3412.14

1 British thermal unit (IT)

1055.06

251.997

2.930 71 × 10−4

1

Pressure

From

To

N/m2(Pa)

kg/cm2

lb/in2

atm

1 newton per square metre (pascal)

1

1.019 72 × 10−5

1.450 38 × 10−4

9.869 23 × 10−6

1 kilogram per square centimetre

980.665 × 102

1

14.2234

0.967 841

1 pound per square inch

6.894 76 × 103

0.070 3068

1

0.068 046

1 atmosphere

1.013 25 × 105

1.03323

14.6959

1