Energy Converter
Convert between joules, calories, kWh, BTU, and more energy units.
Common Energy References
Frequently Asked Questions
What is the difference between a calorie and a Calorie?▼
A lowercase calorie (cal) is the energy needed to raise 1 gram of water by 1°C — a very small unit. A food Calorie (Cal, kcal) is 1,000 calories. Nutrition labels always use kilocalories (kcal), often written as 'Cal' with a capital C.
How many joules in a kilowatt-hour?▼
1 kWh = 3,600,000 joules (3.6 MJ). A watt-hour is the energy used by a 1-watt device running for 1 hour. One kilowatt-hour is what powers a 1000W device for 1 hour, or a 100W bulb for 10 hours.
What is a BTU used for?▼
BTU (British Thermal Unit) is the energy needed to raise 1 pound of water by 1°F. It is commonly used for HVAC systems, furnaces, and air conditioners in the US to measure heating/cooling capacity.
What is an electron-volt?▼
An electron-volt (eV) is the kinetic energy gained by an electron accelerated through 1 volt. It equals 1.602 × 10⁻¹⁹ joules. It is used in atomic physics, chemistry, and particle physics to describe energy at the molecular scale.