Energy Converter
Convert between joules, kilowatt-hours, BTU, calories, and more.
Popular energy conversions
Kilowatt-hours to Joules1 kWh = 3,600,000 J. Multiply kilowatt-hours by 3,600,000 (3.6 million) to get joules. 10 kWh = 36 MJ.Joules to Kilowatt-hours1 J = 2.778×10⁻⁷ kWh. Divide joules by 3,600,000 to convert to kilowatt-hours. 1 MJ = 0.2778 kWh.BTU to Joules1 BTU = 1,055.06 J. Multiply BTUs by 1,055.06 to get joules. A 10,000 BTU AC unit = 10.55 MJ/hour.Calories to Joules1 cal = 4.184 J. Multiply calories by 4.184 to get joules. Note: 1 food Calorie (kcal) = 1,000 cal = 4,184 J.Joules to Calories1 J = 0.239006 cal. Divide joules by 4.184 to convert to thermochemical calories. 1 kJ = 239 cal.BTU to Kilowatt-hours1 BTU = 0.000293071 kWh. Divide BTUs by 3,412.14 to get kilowatt-hours. 10,000 BTU/hr = 2.931 kW.Kilowatt-hours to BTU1 kWh = 3,412.14 BTU. Multiply kilowatt-hours by 3,412.14 to get BTU. A 1 kW heater = 3,412 BTU/hr.
Energy units
Joule
J
Kilojoule
kJ
Megajoule
MJ
Calorie (small)
cal
Kilocalorie
kcal
Watt-hour
Wh
Kilowatt-hour
kWh
BTU
BTU
Foot-pound
ft·lbf
Electronvolt
eV
What is energy?
Energy is the capacity to do work or produce heat.
Common use cases
- Electricity billing (kWh)
- Heating systems (BTU)
- Food energy (kcal)
- Physics and engineering
- Fuel and combustion calculations
Ambiguity notes
Calorie (cal) vs kilocalorie (kcal): food labels say 'Calories' but mean kcal. 1 food Calorie = 1,000 physics calories.
BTU can refer to the International Table BTU (1,055.06 J) or the thermochemical BTU (1,054.35 J). The difference is negligible for most uses.