Energy Converter
Convert between joules, calories, kilowatt-hours and BTU — the units of food labels, electricity bills and physics class.
Quick reference
| Energy | Equals |
|---|---|
| 1 food Calorie (kcal) | 4.184 kJ = 4,184 J |
| 1 kWh | 3.6 MJ ≈ 860 kcal ≈ 3,412 BTU |
| 1 BTU | ≈ 1,055 J ≈ 0.293 Wh |
| A chocolate bar (~250 kcal) | ≈ 1,046 kJ ≈ 0.29 kWh |
Frequently asked questions
Is a food "Calorie" the same as a calorie?
A food Calorie (capital C) is actually a kilocalorie — 1,000 small calories. Food labels in metric countries show kilojoules instead: multiply kcal by 4.184.
What is a kilowatt-hour physically?
The energy a 1,000-watt appliance uses in one hour — a space heater for an hour, or an LED bulb for about four days. It's the unit on your electricity bill.
Where is BTU used?
Mostly in US heating and cooling: furnace outputs and air-conditioner capacities are quoted in BTU per hour. One BTU heats one pound of water by 1 °F.
Last updated: 2026-07-13