Energy
Convert energy units between joules, kilocalories, kilowatt-hours, megajoules and more. Useful for nutrition labels, electricity bills and technical calculations.
Frequently asked questions
1 kilocalorie (kcal) equals 4,184 joules or 4.184 kilojoules. In the US, food labels list energy as "Calories" (capital C), which are kilocalories — so a 200-Calorie snack contains 200 kcal or 836,800 joules.
1 megajoule (MJ) equals 0.2778 kilowatt-hours (kWh). Conversely, 1 kWh equals 3.6 megajoules. Utility companies bill in kWh; scientists and engineers more often work in joules or megajoules.
Energy is the total amount of work done or that can be done (in joules or kWh). Power is the rate at which energy is consumed or produced (in watts = joules per second).
An average US household uses approximately 10,500 kWh of electricity per year according to the US Energy Information Administration (EIA). This is significantly higher than the European average, partly due to air conditioning usage.