# SI Unit Conversions

SI DEFINED UNITS
QuantityNameSymbol
length (distance)meterm
masskilogramkg
timeseconds
temperatureKelvinK
currentAmpereA
quantitymolemol
luminositycandelacd
SI DERIVED UNITS
QuantityNameSymbolUnits
frequencyHertzHzm-1
velocity--m s-1
acceleration--m s-2
forceNewtonNkg m s-2
pressure (stress)PascalPaN m-2 = kg m-1 s-2
energy (work, heat)JouleJN m = kg m2 s-2
momentum (impulse)--N s = kg m s-1
powerWattWJ s -1 = kg m2 s-3
electric chargeCoulombCA s
electric potential (emf)VoltVJ C-1 = W A -1 = kg m2 s-3 A-1
resistanceOhmWV A-1 = kg m2 s-3 A-2
conductanceSiemensSA V-1 = W-1 = kg-1 m-2 s3 A2
magnetic fluxWeberWbV s = kg m2 s-2 A -1
inductanceHenryHWb A-1 = kg m2 s-2 A-2
capacitanceFaradFC V-1 = kg-1 m-2 s4 A2
electric field strength--V m-1 = N C-1
electric displacement--C m-2
magnetic field strength--A m-1
magnetic flux densityTeslaTWb m-2 = N A-1 m-1 = kg s-2 A-1
luminous fluxlumenlmcd sr
illuminanceluxlxlm m²
SI ACCEPTED UNITS
QuantityNameSymbolUnits
lengthÅngstromÅ,å1 a = 10-10 m
volumeLiterL, l1 L = 10-3 m³
massmetric tont1 t = 1000 kg
pressurebarbar1 bar = 105 Pa = 105 N m-2
timeminutemin1 min = 60 sec
timehourh1 h = 60 min = 3600 sec
timedayd1 d = 24 h = 86 400 sec
plane angleminute1’ = (1/60)o = (p/10 800) rad
plane anglesecond"1" = (1/60)’ = (p /648 000) rad
GEOMETRIC CONSTANTS
EARTH CONSTANTS
ConstantSymbolValue
Standard Atmosphereatm101 325 Pa (exact)
Standard Acceleration of Gravityga9.806 65 m s-2 (exact)
Astronomical Unit (Earth-Sun)au1.495 978 706 91 (30) 1011 m
PLANCK CONSTANTS
ConstantSymbolValue
Planck Constanth6.626 075 5 10 (40) 10-34 J s
Planck Constant = h/{e} (in electron Volts)h/{e }4.135 669 2 (12) 10-15 eV s
Planck Constant = h/2ph1.054 572 66 (63) 10-34 J s
Planck Constant = h/2p{e} (in electron Volts)h/{e}6.582 122 0 (20) 10-16 eV s
Planck Mass = (hc/G)1/2mP2.176 71 (14) 10-8 kg
Planck Length = h/mPc = (hG/c3)1/2l P1.616 05 (10) 10-35 m
Planck Time = lP/c = (hG/c5)1/2tP5.390 56 (34) 10 -44 s
RYDBERG CONSTANTS
ConstantSymbolValue
Rydberg Constant = meca²/2h10 973 731.534 (13) m-1
Rydberg Constant = RɎ c (in Hertz)RɎc3.289 841 949 9 (40) 1015 Hz
Rydberg Constant = RɎhc (in Joules)RɎhc2.179 874 1 (13) 10-18 J
Rydberg Constant = RɎ hc/{e} (in electron Volts)RɎhc/{e}13.605 698 1 (40) eV
PHYSICAL CONSTANTS
ConstantSymbolValue
Bohr Radius = a/4pR Ɏao0.529 177 249 (24) 10-10 m
Hartree Energy = e2/4peoao = 2RɎhcEh4.359 748 2 (26) 10-18 J
Hartree Energy = Eh/{e} (in electron Volts)Eh/{e}27.211 396 1 (81) eV
Quantum of Circulation = h/2meh/2me3.636 948 07 (33) 10-4 m2 s-1
Quanta of Circulation = h/m eh/me7.273 896 14 (65) 10-4 m² s-1
CHEMICAL CONSTANTS
ConstantSymbolValue
Avogadro’s numberN A, L6.022 136 7 (36) 1023 mol-1
Atomic Mass Constant = m(12C)/12 = 1 Dalton (Da)mu1.660 540 2 (10) 10-27 kg
Atomic Mass Constant = muc²/{e} (in electron Volts)mu931.494 32 (28) MeV
Faraday ConstantF96 485.309 (29) C mol -1
Molar Planck Constant = NA hNAh3.990 313 23 (36) 10-10 J s mol-1
Molar Planck Constant = NAhcNAhc0.119 626 58 (11) J m mol-1
Molar Gas ConstantR8.314 510 (70) J mol-1 K-1
Molar Volume = RT/p (ideal gas at 1 atm/273.15 K)Vm22 414.10 (19) cm³ mol-1
Loschmidt Constant = NA/Vmno2.686 763 (23) 1025 m³

The 20 SI prefixes used to form decimal multiples and submultiples of SI units are given below:-

FACTORNAMESYMBOL
1024yottaY
1021zettaZ
1018exaE
1015petaP
1012teraT
109gigaG
106megaM
103kilok
102hectoh
10-1decid
10-2centic
10-3millim
10-6micro?
10-9nanon
10-12picop
10-15femtof
10-18attoa
10-21zeptoz
10-24yoctoy

It is important to note that the kilogram is the only SI unit with a prefix as part of its name and symbol. Because multiple prefixes may not be used, in the case of the kilogram the prefix names of Table?5 are used with the unit name "gram" and the prefix symbols are used with the unit symbol "g." With this exception, any SI prefix may be used with any SI unit, including the degree Celsius and its symbol ?C.

Example 1:10-6 kg = 1 mg (one milligram), but not 10-6 kg = 1 ?kg (one microkilogram)

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