Convert between joules, calories, kilocalories, kilowatt-hours, BTU and more. Instant results.
One calorie (small calorie, cal) equals exactly 4.184 joules. Note: the "Calorie" used in food nutrition (with a capital C) is actually a kilocalorie (kcal), which equals 4,184 joules.
To convert kilowatt-hours (kWh) to joules, multiply by 3,600,000. For example, 1 kWh = 3,600,000 joules = 3.6 megajoules. This is because 1 watt = 1 joule/second, and 1 hour = 3,600 seconds.
A BTU (British Thermal Unit) is the amount of heat needed to raise the temperature of 1 pound of water by 1°F. 1 BTU equals approximately 1,055 joules or 0.293 watt-hours. BTUs are commonly used for air conditioning and heating ratings.
A kilocalorie (kcal) equals 1,000 small calories (cal). Food energy is measured in kilocalories, but they are often labeled as "Calories" (capital C) on nutrition labels. So "200 Calories" on a food label means 200 kcal or 200,000 cal.
1 kilowatt-hour (kWh) equals exactly 1,000 watt-hours (Wh). Your electricity bill is measured in kWh — one kWh is the energy used by a 1,000-watt appliance running for 1 hour.