Energy Conversions
6 units · 30 converters
Convert between joules, kilojoules, calories, kilocalories, kilowatt-hours and BTU. Exact factors for nutrition, electricity and heating.
Joule(J)
The joule is the SI unit of energy: the work done by one newton acting over one meter. Food labels in most countries, physics and engineering use joules.
Kilojoule(kJ)
A kilojoule is 1,000 joules, the practical unit for food energy in Australia and Europe and for mechanical work. One kilocalorie equals 4.184 kilojoules.
Calorie(cal)
The small calorie is the energy needed to raise one gram of water by 1 °C, defined as exactly 4.184 joules. It is mostly used in chemistry and heat calculations.
Kilocalorie(kcal)
A kilocalorie equals 1,000 small calories and is the 'Calorie' seen on food labels. An adult needs roughly 2,000–2,500 kcal per day, depending on activity.
Kilowatt-hour(kWh)
A kilowatt-hour is the energy delivered by one kilowatt over one hour, exactly 3.6 million joules. Household electricity bills and EV batteries are measured in kWh.
British Thermal Unit(BTU)
A British thermal unit is the energy to raise one pound of water by 1 °F, about 1,055 joules. Air conditioners, heaters and grills in the US are rated in BTU.