Energy Converter: kWh, kcal, BTU, Joules
Convert energy between kWh, joules, calories, kilocalories, BTU and therms.
Good to know. A kilowatt-hour could lift a small car about 300 metres, and costs about as much as a sweet.
How it works
In plain words
Convert the value into joules, the SI unit of energy, then into the target unit. A kilowatt-hour is 3.6 million joules, a kilocalorie 4,184 joules and a BTU 1,055 joules.
The formula
result = value × (J per "from" unit) ÷ (J per "to" unit) 1 kWh = 3,600,000 J · 1 kcal = 4,184 J · 1 BTU = 1,055.056 J
Worked example
1 kWh is 3,600,000 J, and 3,600,000 ÷ 4,184 = 860.42065 kcal.
Sources
- NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B Exact conversion factors for US customary units.
Sources checked September 30, 2026. 4 automated tests check its answers on every change.
About the energy converter: kwh, kcal, BTU, joules
Energy is measured in different units depending on where it comes from. Electricity is billed in kilowatt-hours, food energy in kilocalories (the “Calories” on food labels) or kilojoules, gas in kilowatt-hours or therms, and heating and cooling in the US in BTU. This converter translates between them, with every unit shown at once.
Everything goes through the joule, the SI unit of energy. A kilowatt-hour is the energy of a 1,000-watt appliance running for an hour: 3.6 million joules. A kilocalorie, the energy to warm a litre of water by 1 °C, is 4,184 joules. The BTU, the energy to warm a pound of water by 1 °F, is about 1,055 joules, and a US therm is 100,000 BTU.
Some comparisons: 1 kWh is about 860 kcal, so a day’s food for an adult, about 2,000 kcal, is roughly 2.3 kWh, about what a tumble dryer uses for one load. A litre of petrol holds about 9 kWh, and an electric car uses about 15 to 20 kWh per 100 km.
The small calorie (cal) and the food Calorie (kcal) differ by a factor of 1,000; food labels mean kilocalories. The thermochemical calorie of exactly 4.184 J is used here.
Questions people ask
How many kcal are in a kWh?
About 860. One kilowatt-hour is 3.6 million joules, and a kilocalorie is 4,184 joules.
How do I convert kcal to kJ?
Multiply by 4.184. A 2,000 kcal diet is about 8,368 kJ.
How many BTU are in a kWh?
About 3,412. One BTU is about 0.000293 kWh.