Energy Converter
Convert between energy units including joules, calories, kilowatt-hours, BTU, and electron volts.
J
All conversions from
Kilojoule
0.001 kJ
Megajoule
0.000001 MJ
Gigajoule
1e-9 GJ
Calorie
0.2390057361 cal
Kilocalorie
0.0002390057 kcal
Watt-hour
0.0002777778 Wh
Kilowatt-hour
2.778e-7 kWh
Megawatt-hour
3e-10 MWh
BTU
0.0009478134 BTU
Therm
9.5e-9 therm
Electronvolt
6.241509e+18 eV
Kiloelectronvolt
6.241509e+15 keV
Megaelectronvolt
6.241509e+12 MeV
Foot-pound
0.7375621493 ft·lbf
Erg
10000000 erg
Frequently Asked Questions
To convert calories to joules, multiply by 4.184. One calorie equals exactly 4.184 joules. For food calories (kcal), multiply by 4,184. For example, 100 calories = 418.4 joules, and 100 kcal = 418,400 joules.
A lowercase calorie (cal) is a small calorie, equal to 4.184 joules. An uppercase Calorie (Cal) or kilocalorie (kcal) is 1,000 small calories. Food labels typically use kilocalories (kcal), often written as Calories in the US.
To convert kilowatt-hours (kWh) to joules, multiply by 3,600,000 (3.6 × 10⁶). One kWh = 3.6 megajoules. For example, 1 kWh of electricity equals 3,600,000 joules of energy.
A BTU (British Thermal Unit) is the energy needed to raise 1 pound of water by 1°F. One BTU equals approximately 1,055.06 joules. BTUs are commonly used for heating/cooling systems in the US, while most of the world uses joules or kilojoules.