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Energy Unit Conversion Calculator

Type values into the field.

kilogram-force metrekgf m
watt secondsW s
kilowatt hourskW h
foot pound-forceft lbf
British thermal unitITBtuIT
newton metreN m

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The capacity for doing work. Energy can exist the following forms: radiation; kinetic energy; potential energy; chemical energy; atomic energy; electromagnetic energy; electrical energy; and heat energy. N m = kg m2 s-2 = CV = V A s = W s = J (Joule).

There can be some confusion in some of the units of energy. The calorie can take 5 different values and, while these do not vary by very much, for accurate work it is necessary to specify which calorie is being used. The 5 calories are known as the:
  • International Table calorie = cal(IT) = 4.1868 J
  • thermochemical calorie = cal(th) = 4.184 J
  • mean calorie = cal(mean) = 4.190 02 J
  • 15 degree C calorie = cal(15C) = 4.185 80 J
  • 20 degree C calorie = cal(20C) = 4.181 90 J.

Unless a clear statement is made saying otherwise, assume the IT calorie is being used. As a further complication, in working with food and expressing nutritional values, the unit of a Calorie (capital C) is often used to represent 1000 calories, and again it is necessary to specify which calorie is being used for that. The British thermal unit (Btu) can also take different values and they are named in a similar way to the calorie. Also note that the therm is 100 000 Btu so its exact size depends on which Btu is being used.
British thermal units:
  • Btu(IT) = 1055.056 J
  • Btu (th) = 1054.350 J
  • Btu (mean) = 1055.87J