# Physical Constants, Prefixes, and Conversion Factors

Here are some useful physical constants, conversion factors, and unit prefixes. They are used in many calculations in chemistry, as well as in physics and other sciences.

Useful Constants

 Acceleration of Gravity 9.806 m/s2 Avogadro’s Number 6.022 x 1023 Electronic Charge 1.602 x 10-19 C Faraday Constant 9.6485 x 104 J/V Gas Constant 0.08206 L·atm/(mol·K)8.314 J/(mol·K)8.314 x 107 g·cm2/(s2·mol·K) Planck’s Constant 6.626 x 10-34 J·s Speed of Light 2.998 x 108 m/s p 3.14159 e 2.718 ln x 2.3026 log x 2.3026 R 19.14 J/(mol·K) 2.3026 RT (at 25°C) 5.708 kJ/mol

Common Conversion Factors

QuantitySI UnitOther UnitConversion Factor
Energyjoulecalorie
erg
1 cal = 4.184 J
1 erg = 10-7 J
Forcenewtondyne1 dyn = 10-5 N
LengthmetreAngstrom1 Å = 10-10 m = 10-8 cm = 10-1 nm
Masskilogrampound1 lb = 0.453592 kg
Pressurepascalbar
atmosphere
mm Hg
lb/in2
1 bar = 105 Pa
1 atm = 1.01325 x 105 Pa
1 mm Hg = 133.322 Pa
1 lb/in2 = 6894.8 Pa
TemperaturekelvinCelsius
Fahrenheit
1°C = 1 K
1°F = 5/9 K
Volumecubic metrelitre
gallon (U.S.)
gallon (U.K.)
cubic inch
1 L = 1 dm3 = 10-3 m3
1 gal (U.S.) = 3.7854 x 10-3 m3
1 gal (U.K.) = 4.5641 x 10-3 m3
1 in3 = 1.6387 x 10-6 m3

SI Unit Prefixes

FactorsPrefixSymbol
1012teraT
199gigaG
106megaM
103kilok
102hectoh