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Metric System Imperial System
Joule [J] foot-poundal [ft pdl]
Kilojoule [kJ] inch-pound force [in lbf]
Kilogram-meter [KGm] foot-pound force [ft lbf]
Watt hour [Wh] horsepower-hour [hph]
Kilowatt hour [kWh] BTU**
Erg [erg] Atomic
Calories Electronvolt [eV]
Calorie [cal] * Hartree [Eh]
Kilocalorie [kcal] Rydberg [Ry]
*International Steam Table Calorie (1956) (calIT) equals exactly 4.1868J
**Most widely used BTU definition based on International Steam Table Calorie (1956)
Joule - Energy Unit
Unit of energy in the International System Of Units (SI) is Joule. Joule is the derived unit. Joule formula: 1 J = 1 N · m = 1 kg · m2 / s2

One joule is the amount of energy required to perform the following actions (
  • The work done by a force of one newton traveling through a distance of one meter;
  • The work required to move an electric charge of one coulomb through an electrical potential difference of one volt; or one coulomb volt, with the symbol C·V;
  • The work done to produce power of one watt continuously for one second; or one watt second (compare kilowatt hour), with the symbol W·s. Thus a kilowatt hour is 3,600,000 joules or 3.6 megajoules;
  • The kinetic energy of a 2 kg mass moving at a velocity of 1 m/s.
Joule to calorie formula: Based on International Steam Table (1956) 1 calorie is defined to be exactly 4.1868J. Ergo:

1 cal = 4.1868J => N calories = N*4.1868 J
1 J = 0.238846 cal => N joules = N*0.238846 calories.

UnitIn Joules
Metric System
Joule [J]1
Kilojoule [kJ]1000
Kilogram meter [KGm]9.80665
Watt hour [Wh]3600
Kilowatt hour [kWh]3600000
Erg [erg]1e-7
Imperial System
foot-poundal [ft pdl]0.0421401100938
inch-pound force [in lbf]0.1129848290276167
foot-pound force [ft lbf]1.3558179483314004
horsepower-hour [hph]2.6845e+6
Calories [cal]4.1868
Kilocalories [kcal]4186.8
Electronvolt [eV]1.6021765314e-19
Hartree [Eh]4.3597441775e-18
Rydberg [Ry]2.179872e-18

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