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Energy Converter

56 conversions available

Convert between joules, calories, kilowatt-hours, BTU and more.

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Joules → Kilojoules Joules → Calories Joules → Kilocalories Joules → Kilowatt-hours Joules → Watt-hours Joules → BTU Joules → Electron Volts Kilojoules → Joules Kilojoules → Calories Kilojoules → Kilocalories Kilojoules → Kilowatt-hours Kilojoules → Watt-hours Kilojoules → BTU Kilojoules → Electron Volts Calories → Joules Calories → Kilojoules Calories → Kilocalories Calories → Kilowatt-hours Calories → Watt-hours Calories → BTU Calories → Electron Volts Kilocalories → Joules Kilocalories → Kilojoules Kilocalories → Calories Kilocalories → Kilowatt-hours Kilocalories → Watt-hours Kilocalories → BTU Kilocalories → Electron Volts Kilowatt-hours → Joules Kilowatt-hours → Kilojoules Kilowatt-hours → Calories Kilowatt-hours → Kilocalories Kilowatt-hours → Watt-hours Kilowatt-hours → BTU Kilowatt-hours → Electron Volts Watt-hours → Joules Watt-hours → Kilojoules Watt-hours → Calories Watt-hours → Kilocalories Watt-hours → Kilowatt-hours Watt-hours → BTU Watt-hours → Electron Volts BTU → Joules BTU → Kilojoules BTU → Calories BTU → Kilocalories BTU → Kilowatt-hours BTU → Watt-hours BTU → Electron Volts Electron Volts → Joules Electron Volts → Kilojoules Electron Volts → Calories Electron Volts → Kilocalories Electron Volts → Kilowatt-hours Electron Volts → Watt-hours Electron Volts → BTU

Most popular energy conversions

The most searched energy conversions are calories to joules, kWh to joules, and BTU to joules. One calorie is 4.184 joules, one kilowatt-hour is 3.6 million joules, and one BTU is about 1,055 joules. Note that food 'calories' are actually kilocalories.

Understanding energy units

Energy takes many units by context: joules in physics, kilocalories on food labels, kilowatt-hours on electricity bills, and BTU in heating and cooling. One food calorie equals 1,000 physics calories (a kilocalorie), a frequent source of confusion.

Quick reference

1 calorie = 4.184 J · 1 kcal = 4,184 J · 1 kWh = 3,600,000 J · 1 BTU = 1,055 J. Use the converter for any exact value.

Quick reference: common energy conversions

1 kilowatt-hour	3.6 MJ (860 kcal)
1 kilocalorie	4.184 kJ
1 BTU	1,055 J
1 therm	29.3 kWh
1 joule	0.239 calories
Daily 2,000 kcal diet	≈ 2.3 kWh
Fridge (modern)	≈ 1 kWh/day
EV consumption	15–20 kWh / 100 km

Frequently asked questions

What exactly is a kilowatt-hour?

The energy of running a 1,000-watt appliance for one hour — 3.6 million joules. Kilowatts × hours × your tariff gives the cost of running anything.

Are food calories the same as physics calories?

Food 'calories' are kilocalories: 1 food Cal = 1,000 small calories = 4,184 joules. A 500-calorie meal is about 2.1 megajoules.

What is a BTU?

The British Thermal Unit (1,055 J) — the energy to heat one pound of water by 1°F. It survives in air-conditioner and heater ratings, where BTU/h describes heating or cooling power.