Energy
Convert energy units between joules, kilocalories, kilowatt-hours, megajoules and more. Useful for food labels, electricity bills and technical calculations.
Frequently asked questions
1 kilocalorie (kcal) equals 4,184 joules or 4.184 kilojoules. Kilocalories appear on food labels to indicate energy content — also written as "Calories" (capital C) in English-speaking countries.
1 megajoule (MJ) equals 0.2778 kilowatt-hours (kWh). Conversely, 1 kWh equals 3.6 megajoules. Energy suppliers 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 UK household uses approximately 3,300 kWh of electricity per year. This excludes gas consumption and can vary considerably depending on the number of occupants and home insulation.