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Constants and SI units


Table 1: SI Base Units

Length metre m
Mass kilogram kg
Time second s
Electric Current ampere A
Thermodynamic Temperature kelvin K
Amount of Substance mole mol
Luminous Intensity candela cd

Table 2: SI Derived Units

Area square metre m2
Volume cubic metre m3
Speed/Velocity metre per second m s-1
Acceleration metre per second squared m s-2
Wave Number reciprocal metre m-1
Density/Mass Density kilogram per cubic metre kg m-3
Specific Volume cubic metre per kilogram m3kg-1
Current Density ampere per square metre A m-2
Magnetic Field Strength ampere per metre A m-1
Concentration mole per cubic metre mol m-3
Luminance candela per square metre cd m-2

Table 3: SI Derived Units With Special Names

DimensionNameSymbolStandard UnitsBase Units
Frequency hertz Hz   s-1
Force newton N   kg m s-2
Pressure/Stress pascal Pa N m-2 kg m-1 s-2
Energy/Work/Quantity of Heat joule J N m kg m2 s-2
Power watt W J s-1 kg m2 s-3
Electric Charge coulomb C   A s
Voltage volt V W A-1 kg m2 s-3 A-1
Capacitance farad F C V-1 kg-1 m-2 s4 A2
Inductance henry H   A-2 kg m2 s-2
Electric Resistance ohm   V A-1 kg m2 s-3 A-2
Celsius Temperature degree celsius C   K
Activity of a Radionuclide becquerel Bq   s-1
Dynamic Viscosity pascal second   Pa s kg m-1 s-1
Moment of Force newton meter   N m kg 
Heat Capacity/Entropy joule per kelvin   J K-1 kg m2 s-2 K-1 
Specific Heat Capacity/Specific Entropy joule per kilorgam kelvin   J kg-1 K-1  m2 s-2 K-1 
Specific Energy joule per kilogram   J kg-1  m2 s-2 
Thermal Conductivity watt per metre kelvin   W m-1 K-1  kg m s-3 K-1 
Energy Density joule per cubic metre   J m-3  kg m-1 s-2 
Electric Field Strength volt per metre   V m-1  kg m s-3 A-1 

Table 4: A selection of physical constants from CODATA 2006

Name Symbol Value
acceleration due to gravity (exact) g 9.806 65 ms2
unified atomic mass unit u 1.660 538 782(83) x 10-27 kg
Avogadro constant NA 6.022 141 79(30) x 1023 mol-1
Bohr magneton μB 9.274 009 15(23) x 10-24 J T-1
Bohr radius ao 5.291 772 0859(36) x 10-11 m
Boltzmann constant k 1.380 650 4(24) x 10-23 J K-1
electron charge magnitude e 1.602 176 487(40) x 10-19 C
electron mass me 9.109 382 15(45) x 10-31 kg
fine structure constant α 7.297 352 5376(50) x 10-3
inverse fine structure constant 1/α 137.035 999 679(94)
gravitational constant G 6.674 28(67) x 10-11 m3 kg-1 s-2
nuclear magneton μN 5.050 783 24(13)x 10-27 J T-1
permeability of free space μ0 4 π x 10-7 N A-2
permittivity of free space e0 8.854 187 817... x 10-12 F m-1
pi π 3.141 592 653...
Planck constant h 6.626 068 96(33) x 10-34 J s
proton (1H) mass mp 1.672 621 637(83) x 10-27 kg
speed of light in vacuum (exact) c 299 792 458 ms-1
Stefan-Boltzmann constant σ 5.670 400(40) x 10-8 W m-2 K-4