Physical Constants, Prefixes, and Conversion Factors

Look Up Useful Constants and Conversions

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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 Gravity9.806 m/s2
Avogadro's Number6.022 x 1023
Electronic Charge1.602 x 10-19 C
Faraday Constant9.6485 x 104 J/V
Gas Constant0.08206 L·atm/(mol·K)
8.314 J/(mol·K)
8.314 x 107 g·cm2/(s2·mol·K)
Planck's Constant6.626 x 10-34 J·s
Speed of Light2.998 x 108 m/s
p3.14159
e2.718
ln x2.3026 log x
2.3026 R19.14 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
Lengthmetre or meterångström1 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

Metric system or SI units are based on factors of ten. However, most units prefixes with names are 1000 times apart. The exception are near the base unit (centi-, deci-, deca-, hecto-). Usually, a measurement is reported using a unit with one of these prefixes.

FactorsPrefixSymbol
1012teraT
199gigaG
106megaM
103kilok
102hectoh
101decada
10-1decid
10-2centic
10-3millim
10-6microµ
10-9nanon
10-12picop
10-15femtof
10-18attoa