SI Unit
(Abbreviation)
|
Typical symbol
|
quantity
|
Mechanical
|
||
meter, m
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x,y,z,l,d
|
Length
|
kilogram, kg
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m
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Mass
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second, s
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t
|
Time
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meter/second, m/s
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v, u
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Velocity
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newton, n
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f
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Force
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newton-meter, nm
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t
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Torque
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pascal, pa
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p
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Pressure
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joule, j
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w
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Energy
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watt, w
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p,p
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Power
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radian, rad
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α,β,γ,θ
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Angle
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radian/second, rad/s
|
ω
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Angular velocity
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Kg-m2
|
J
|
Mass polar moment of inertia
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Electrical
|
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coulomb, C
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q, Q
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Charge
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ampere, A
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i,I
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(Electric) current
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volt, V
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v,V,e,E
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Voltage
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hertz, Hz
|
f
|
Frequency
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radian per second, rad/s
|
ω
|
Radian frequency
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voltampere, VA
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S
|
Apparent power
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watt, W
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P
|
Average power
|
voltampere-reactive, var
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Q
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Reactive power
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ohm, Ω
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R
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Resistance
|
henry, H
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L
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Inductance
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farad, F
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C
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Capacitance
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ohm, Ω
|
Z , X
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Impedance, reactance
|
siemens, S
|
G
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Conductance
|
siemens, S
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Y, B
|
Admittance, susceptance
|
Thermal
|
||
kelvin, K
|
,θT
|
Temperature
|
watt, W
|
P, Q
|
Thermal power
|
joule, J
|
W
|
Heat energy
|
joule/kelvin, J/K
|
C
|
Thermal capacitance
|
watt/kelvin, W/K
|
G
|
Thermal capacitance
|
joule/(kelvin-kilogram), J/(K-kg)
|
cp
|
Specific heat
|
Magnetic
|
||
weber, Wb
|
φ
|
Flux
|
tesla, T
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B
|
Flux density
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ampere/meter, A/m
|
H
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Magnetic field intensity
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1/henry, H-1
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ℜ
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Reluctance
|
henry, H
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℘
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Permeance
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ampere-turns, A
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ℑ
|
Magnetomotive force
|
SI Prefixes
|
|||||
10-24
|
y
|
yocto
|
1024
|
Y
|
yotta
|
10-21
|
z
|
zepto
|
1021
|
Z
|
zetta
|
10-18
|
a
|
atto
|
1018
|
E
|
exa
|
10-15
|
f
|
femto
|
1015
|
P
|
peta
|
10-12
|
p
|
pico
|
1012
|
T
|
tera
|
10-9
|
n
|
nano
|
109
|
G
|
giga
|
10-6
|
μ
|
micro
|
106
|
M
|
mega
|
10-3
|
m
|
milli
|
103
|
k
|
kilo
|
10-2
|
c
|
centi
|
102
|
h
|
hecto
|
10-1
|
d
|
deci
|
101
|
da
|
Deca or deka
|
Example
usage: I= 118 A = 0.118 kA = 118000 mA.
|
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Selected Constants
Permeability of free space = 0.4 π μH/m
Permittivity of free space = 8.8542 pf/m
Absolute zero (temperature) = 0 K = −273.2°C = −459.7°F = 0°R
Freezing point of water = 273.2 K = 0°C = 32°F = 491.7°R
g = acceleration of gravity = 9.807 m/s2 = 32.17 ft/s2
G = gravitational constant = 66.72 pN (m2) (kg-2)
c = speed of light in vacuum = 0.2998 m/ns = 299.8 km/s
Avogadro’s constant = 1.602 × 1023 = molecules per mole
e = charge on electron = 0.1602 aC
m0 = electron rest mass = 9.11 × 10-28 gram
1 revolution = 2π radians = 360 degrees
1 standard atmosphere (atm) = 760 mm Hg = 101.3 kPa = 29.92 in Hg =
14.696 psi
Air density = 1.225 kg/m3@ 1 atmosphere, 15°C, 1 u = 1 amu = 1 atomic
mass unit = 1.661 × 10-27 kg
1 toe (1 tonne oil equivalent) = 41.868 GJ = 1270 m3 natural gas (STP) = 2.3 tonnes coal
Permittivity of free space = 8.8542 pf/m
Absolute zero (temperature) = 0 K = −273.2°C = −459.7°F = 0°R
Freezing point of water = 273.2 K = 0°C = 32°F = 491.7°R
g = acceleration of gravity = 9.807 m/s2 = 32.17 ft/s2
G = gravitational constant = 66.72 pN (m2) (kg-2)
c = speed of light in vacuum = 0.2998 m/ns = 299.8 km/s
Avogadro’s constant = 1.602 × 1023 = molecules per mole
e = charge on electron = 0.1602 aC
m0 = electron rest mass = 9.11 × 10-28 gram
1 revolution = 2π radians = 360 degrees
1 standard atmosphere (atm) = 760 mm Hg = 101.3 kPa = 29.92 in Hg =
14.696 psi
Air density = 1.225 kg/m3@ 1 atmosphere, 15°C, 1 u = 1 amu = 1 atomic
mass unit = 1.661 × 10-27 kg
1 toe (1 tonne oil equivalent) = 41.868 GJ = 1270 m3 natural gas (STP) = 2.3 tonnes coal
1 ton TNT = 4.184 GJ
Selected Conversion Factors
1 inch = 2.54 cm; 1 foot = 12 inches; 1 meter = 3.28084 feet
1 pound force (lbf)= 4.4482 newtons; 1 kilogram = 2.188 pound mass (lbm)
J in kg-m2 = 0.0.04246 × J in lbm-ft2
1 atomic mass unit = u = 1.661 × 10-27 kg
Electron/positron mass = 0.000549 u
Proton mass = 1.007276 u
Neutron mass = 1.008665 u
1 slug = 14.59 kilogram
1 foot-pound = 1.356 newton-meter
1 horsepower = 746 watts
1 British Thermal Unit (BTU) = 1055 joule
1 calorie = 4.19 joule
Temperature in Kelvin (K) = TK
Temperature in degrees Celsius (°C) = TC = TK – 273.2
Temperature in degrees Fahrenheit (°F) = TF = 1.8TC + 32
Temperature in degrees Rankine (°R) = TR = TF + 459.7
1 milligauss = 1 mG = 0.1 microtesla = 0.1 μT
1 ton (refrigeration) = 3517 watts = 12 kBTU/hr
1 tonne = 1 metric ton = 1000 kg
Speed in rad/s = (2π/60) × speed in rpm (rpm = revolutions per minute)
1 day = 24 hours; 1 hour = 60 minutes; 1 minute = 60 seconds
1 nautical mile = 6000 ft = 1.1364 mile
1 knot = 1 nautical mile per hour = 1.1364 mph = 0.5080 m/s
1 pound force (lbf)= 4.4482 newtons; 1 kilogram = 2.188 pound mass (lbm)
J in kg-m2 = 0.0.04246 × J in lbm-ft2
1 atomic mass unit = u = 1.661 × 10-27 kg
Electron/positron mass = 0.000549 u
Proton mass = 1.007276 u
Neutron mass = 1.008665 u
1 slug = 14.59 kilogram
1 foot-pound = 1.356 newton-meter
1 horsepower = 746 watts
1 British Thermal Unit (BTU) = 1055 joule
1 calorie = 4.19 joule
Temperature in Kelvin (K) = TK
Temperature in degrees Celsius (°C) = TC = TK – 273.2
Temperature in degrees Fahrenheit (°F) = TF = 1.8TC + 32
Temperature in degrees Rankine (°R) = TR = TF + 459.7
1 milligauss = 1 mG = 0.1 microtesla = 0.1 μT
1 ton (refrigeration) = 3517 watts = 12 kBTU/hr
1 tonne = 1 metric ton = 1000 kg
Speed in rad/s = (2π/60) × speed in rpm (rpm = revolutions per minute)
1 day = 24 hours; 1 hour = 60 minutes; 1 minute = 60 seconds
1 nautical mile = 6000 ft = 1.1364 mile
1 knot = 1 nautical mile per hour = 1.1364 mph = 0.5080 m/s
Temperature Scales
Kelvin
|
Centigrade
|
Rankine
|
Fahrenheit
|
373
K
|
100°C
|
672°R
|
212°F
|
311
K
|
38°C
|
560°R
|
212°F
|
273
K
|
0°C
|
492°R
|
32°F
|
255
K
|
−18°C
|
460°R
|
0°F
|
0
K
|
−273°C
|
0°R
|
−460°F
|
Notes
One unit C = one unit K; one unit F = one unit R; one unit K = I.8 F units.
Absolute zero (0 K) = −459.67°F = −273.15°C.
Normal human body temperature is 98.2°F (36.8°C).
One unit C = one unit K; one unit F = one unit R; one unit K = I.8 F units.
Absolute zero (0 K) = −459.67°F = −273.15°C.
Normal human body temperature is 98.2°F (36.8°C).