Energy Converter
Convert energy between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, foot-pounds, and electronvolts.
Convert
Joules
3,600,000 J
Kilojoules
3,600 kJ
Calories
860,420.65 cal
Kilocalories
860.4207 kcal
Watt-hours
1,000 Wh
Kilowatt-hours
1 kWh
British Thermal Units
3,412.13 BTU
Foot-pounds
2,655,219.72 ft·lbf
Electronvolts
2.2469e+25 eV
Frequently Asked Questions about the Energy Converter
What is the difference between a calorie and a kilocalorie?
A calorie (cal) is the energy needed to raise 1 gram of water by 1 °C. A kilocalorie (kcal) is 1,000 calories. Food labels often write Calorie (capital C) but mean kilocalorie. So a 250 Calorie snack is actually 250 kcal, or 1,046 kJ.
Why are food labels in kcal but exercise apps in calories?
Food labels in the US and EU use kcal (often shown as Calories). Many fitness apps display the same number and just call it calories. They refer to the same value. 1 food Calorie = 1 kcal = 1,000 small calories = 4,184 J.
What does kWh mean on my electricity bill?
A kilowatt-hour (kWh) is the energy used by a 1,000-watt device running for one hour. It equals 3.6 million joules. If your bill shows 300 kWh, you used 1.08 billion joules that month, or about 258,000 kcal.
Why is BTU used for air conditioners and heaters?
British Thermal Units measure heating and cooling capacity, especially in North America. 1 BTU = 1,055.06 J. A 12,000 BTU/h AC removes about 3.5 kW of heat, enough to cool a room of 250 to 400 square feet.
What is an electronvolt and when is it used?
An electronvolt (eV) is the tiny amount of energy an electron gains when accelerated by 1 volt. It equals 1.602e-19 J. Physicists use it for atomic and particle energies, like photon energies in light (around 2 to 3 eV for visible light).