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 Physical Constants, Prefixes, and Conversion Factors
Handy Reference Information

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

Quantity SI Unit Other Unit Conversion Factor
Energy joule calorie
erg
1 cal = 4.184 J
1 erg = 10-7 J
Force newton dyne 1 dyn = 10-5 N
Length metre ångström 1 Å = 10-10 m = 10-8 cm = 10-1 nm
Mass kilogram pound 1 lb = 0.453592 kg
Pressure pascal bar
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
Temperature kelvin Celsius
Fahrenheit
1°C = 1 K
1°F = 5/9 K
Volume cubic metre litre
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

Factors Prefix Symbol
1012 tera T
199 giga G
106 mega M
103 kilo k
102 hecto h
101 deca da
10-1 deci d
10-2 centi c
10-3 milli m
10-6 micro µ
10-9 nano n
10-12 pico p
10-15 femto f
10-18 atto a

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Anne Marie Helmenstine, Ph.D.