SI units

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SI units (Système International d'Unités) pl. n. the internationally agreed system of units, based on the metre-kilogram-second system, now in use for all scientific purposes.

Table 11.1 Base and supplementary SI units

Physical quantity

Name of unit

Symbol for 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

*supplementary units

Table 11.2 Derived SI units with special names

Physical quantity

Name of unit

Symbol for 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 (illumination)

lux

lx

absorbed dose

gray

Gy

activity

becquerel

Bq

dose equivalent

sievert

Sv

Table 11.3 Decimal multiples and submultiples to be used with SI units

Submultiple

Prefix

Symbol

Multiple

Prefix

Symbol

10−1

deci

d

101

deca

da

10−2

centi

c

102

hecto

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

10−16

atto

a

1016

exa

E

10−21

zepto

z

1021

zetta

Z

10−24

yocto

y

1024

yotta

Y

Table 11.4 Conversion of units to and from SI units

From

To

Multiply by

Temperature conversion

°C (Celsius) = 5/9(°F − 32)

°F (Fahrenheit) = (9/5 × °C) + 32

in

m

0.0254

ft

m

0.3048

sq in

m2

0.00064516

sq ft

m2

0.092903

cu in

m3

0.0000164

cu ft

m3

0.0283168

l(itre)

m3

0.001

gal(lon)

m3

0.0045609

gal(lon)

litres

4.5609

lb

kg

0.453592

g cm−3

kg m−3

1000

lb/in3

kg m−3

27679.9

mmHg

Pa

133.322

cal

J

4.1868

m

in

39.3701

cm

in

0.393701

cm2

sq in

0.155

m2

sq in

1550

m2

sq ft

10.7639

m3

cu in

61023.6

m3

cu ft

35.3146

m3

l(itre)

1000

m3

gal(lon)

219.969

kg

lb

2.20462

kg m−3

g cm−3

0.001

kg m−3

lb/in3

0.0000363

Pa

mmHg

0.0075006

J

cal

0.238846


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