Convert energy, instantly.
Joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours and BTU — for food labels, bills and physics.
Energy Converter
Energy conversion benchmarks
⚡ Energy
| 1 kcal | 4,184 J |
| 1 kWh | 3,600,000 J |
| 1 BTU | 1,055.06 J |
| 1 kWh | 3,412.14 BTU |
How this conversion works
Energy conversions here run through the joule as the SI base unit. Food labels in most countries use kilocalories (often just labeled 'Calories' with a capital C, which is a common source of confusion — a food 'Calorie' is actually a kilocalorie, i.e. 1,000 small calories).
Electricity bills are usually metered in kilowatt-hours (kWh), a unit of energy despite the 'watt' in its name — it's the energy used by a 1,000-watt appliance running for one hour. BTU (British Thermal Unit) commonly appears on air conditioner and heater specifications, especially in the US.
Frequently asked questions
Is a food 'Calorie' the same as a science-class calorie?
No — a food Calorie (capital C, as printed on nutrition labels) is actually a kilocalorie, equal to 1,000 small calories (lowercase c) as used in chemistry. This converter's 'Calories' and 'Kilocalories' units are the same size for that reason.
How many kWh does a typical appliance use?
It depends entirely on the appliance's wattage and how long it runs — a 100-watt device running for 10 hours uses 1 kWh. Check the appliance's rated wattage and multiply by hours used, then divide by 1,000.