Energy conversions
Energy converter for SI and specialist units — joules, kilojoules, megajoules, kilowatt-hours, calories, kilocalories, British Thermal Units (BTU), electronvolts, watt-hours and therms. Essential for nutrition, electricity bills, HVAC and physics.
The SI base unit of energy — 1 newton-metre
Joule to Kilojoule
1 J = 0.001 kJ
Joule to Megajoule
1 J = 1.0000e-6 MJ
Joule to Kilowatt-Hour
1 J = 2.7778e-7 kWh
Joule to Watt-Hour
1 J = 0.0002778 Wh
Joule to Calorie
1 J = 0.239 cal
Joule to Kilocalorie
1 J = 0.000239 kcal
Joule to British Thermal Unit
1 J = 0.0009478 BTU
Joule to Electronvolt
1 J = 6.2415e18 eV
Joule to Therm
1 J = 9.4782e-9 thm
The European nutrition-label energy unit — required alongside kcal
Kilojoule to Joule
1 kJ = 1,000 J
Kilojoule to Megajoule
1 kJ = 0.001 MJ
Kilojoule to Kilowatt-Hour
1 kJ = 0.0002778 kWh
Kilojoule to Watt-Hour
1 kJ = 0.2778 Wh
Kilojoule to Calorie
1 kJ = 239.006 cal
Kilojoule to Kilocalorie
1 kJ = 0.239 kcal
Kilojoule to British Thermal Unit
1 kJ = 0.9478 BTU
Kilojoule to Electronvolt
1 kJ = 6.2415e21 eV
Kilojoule to Therm
1 kJ = 9.4782e-6 thm
Used for fuel energy content and large-scale energy accounting
Megajoule to Joule
1 MJ = 1,000,000 J
Megajoule to Kilojoule
1 MJ = 1,000 kJ
Megajoule to Kilowatt-Hour
1 MJ = 0.2778 kWh
Megajoule to Watt-Hour
1 MJ = 277.778 Wh
Megajoule to Calorie
1 MJ = 239,005.74 cal
Megajoule to Kilocalorie
1 MJ = 239.006 kcal
Megajoule to British Thermal Unit
1 MJ = 947.817 BTU
Megajoule to Electronvolt
1 MJ = 6.2415e24 eV
Megajoule to Therm
1 MJ = 0.009478 thm
The standard electricity-bill unit — 1 kW × 1 hour
Kilowatt-Hour to Joule
1 kWh = 3,600,000 J
Kilowatt-Hour to Kilojoule
1 kWh = 3,600 kJ
Kilowatt-Hour to Megajoule
1 kWh = 3.6 MJ
Kilowatt-Hour to Watt-Hour
1 kWh = 1,000 Wh
Kilowatt-Hour to Calorie
1 kWh = 860,420.65 cal
Kilowatt-Hour to Kilocalorie
1 kWh = 860.421 kcal
Kilowatt-Hour to British Thermal Unit
1 kWh = 3,412.14 BTU
Kilowatt-Hour to Electronvolt
1 kWh = 2.2469e25 eV
Kilowatt-Hour to Therm
1 kWh = 0.03412 thm
The small-battery capacity unit — 1 W × 1 hour
Watt-Hour to Joule
1 Wh = 3,600 J
Watt-Hour to Kilojoule
1 Wh = 3.6 kJ
Watt-Hour to Megajoule
1 Wh = 0.0036 MJ
Watt-Hour to Kilowatt-Hour
1 Wh = 0.001 kWh
Watt-Hour to Calorie
1 Wh = 860.421 cal
Watt-Hour to Kilocalorie
1 Wh = 0.8604 kcal
Watt-Hour to British Thermal Unit
1 Wh = 3.41214 BTU
Watt-Hour to Electronvolt
1 Wh = 2.2469e22 eV
Watt-Hour to Therm
1 Wh = 3.4121e-5 thm
The scientific gram calorie — 4.184 joules
Calorie to Joule
1 cal = 4.184 J
Calorie to Kilojoule
1 cal = 0.004184 kJ
Calorie to Megajoule
1 cal = 4.1840e-6 MJ
Calorie to Kilowatt-Hour
1 cal = 1.1622e-6 kWh
Calorie to Watt-Hour
1 cal = 0.001162 Wh
Calorie to Kilocalorie
1 cal = 0.001 kcal
Calorie to British Thermal Unit
1 cal = 0.003966 BTU
Calorie to Electronvolt
1 cal = 2.6114e19 eV
Calorie to Therm
1 cal = 3.9657e-8 thm
The food-energy unit — 1 kcal = 4184 J (the nutrition "Calorie")
Kilocalorie to Joule
1 kcal = 4,184 J
Kilocalorie to Kilojoule
1 kcal = 4.184 kJ
Kilocalorie to Megajoule
1 kcal = 0.004184 MJ
Kilocalorie to Kilowatt-Hour
1 kcal = 0.001162 kWh
Kilocalorie to Watt-Hour
1 kcal = 1.16222 Wh
Kilocalorie to Calorie
1 kcal = 1,000 cal
Kilocalorie to British Thermal Unit
1 kcal = 3.96567 BTU
Kilocalorie to Electronvolt
1 kcal = 2.6114e22 eV
Kilocalorie to Therm
1 kcal = 3.9657e-5 thm
The US HVAC energy unit — 1055 joules
British Thermal Unit to Joule
1 BTU = 1,055.06 J
British Thermal Unit to Kilojoule
1 BTU = 1.05506 kJ
British Thermal Unit to Megajoule
1 BTU = 0.001055 MJ
British Thermal Unit to Kilowatt-Hour
1 BTU = 0.0002931 kWh
British Thermal Unit to Watt-Hour
1 BTU = 0.2931 Wh
British Thermal Unit to Calorie
1 BTU = 252.164 cal
British Thermal Unit to Kilocalorie
1 BTU = 0.2522 kcal
British Thermal Unit to Electronvolt
1 BTU = 6.5851e21 eV
British Thermal Unit to Therm
1 BTU = 1.0000e-5 thm
The particle physics energy unit — 1.602 × 10⁻¹⁹ joules
Electronvolt to Joule
1 eV = 1.6022e-19 J
Electronvolt to Kilojoule
1 eV = 1.6022e-22 kJ
Electronvolt to Megajoule
1 eV = 1.6022e-25 MJ
Electronvolt to Kilowatt-Hour
1 eV = 4.4505e-26 kWh
Electronvolt to Watt-Hour
1 eV = 4.4505e-23 Wh
Electronvolt to Calorie
1 eV = 3.8293e-20 cal
Electronvolt to Kilocalorie
1 eV = 3.8293e-23 kcal
Electronvolt to British Thermal Unit
1 eV = 1.5186e-22 BTU
Electronvolt to Therm
1 eV = 1.5186e-27 thm
The US and UK gas-billing unit — 100,000 BTU
Therm to Joule
1 thm = 105,505,585.3 J
Therm to Kilojoule
1 thm = 105,505.59 kJ
Therm to Megajoule
1 thm = 105.506 MJ
Therm to Kilowatt-Hour
1 thm = 29.3071 kWh
Therm to Watt-Hour
1 thm = 29,307.11 Wh
Therm to Calorie
1 thm = 25,216,440.08 cal
Therm to Kilocalorie
1 thm = 25,216.44 kcal
Therm to British Thermal Unit
1 thm = 100,000 BTU
Therm to Electronvolt
1 thm = 6.5851e26 eV
Tips for energy conversions
1 kWh (kilowatt-hour) is the most common unit on electricity bills. UK household average: 2900 kWh/year.
Nutrition labels in Europe show both kJ and kcal (1 kcal = 4.184 kJ). An adult daily intake is about 2000 kcal = 8400 kJ.
BTU (British Thermal Unit) is used for HVAC and boiler ratings, mainly in the US.
The electronvolt (eV) is the energy unit of particle physics — 1 eV = 1.602 × 10⁻¹⁹ J.
Common mistakes to avoid
Confusing calorie (scientific) with Calorie or kcal (nutrition). Food "calories" are actually kilocalories.
Mixing kWh (energy) with kW (power) on electricity specs.
Using BTU without specifying Btu/h (power) vs BTU (energy).
Treating joule and watt as interchangeable — joule is energy, watt is power (J/s).
Learn about each unit
Full encyclopedia page for every energy unit — definition, history, uses, tips.