Energy Converter
Convert between joules, calories, watt-hours, BTU, electron volts and more
How Energy Conversion Works
Energy measures the ability to do work. The joule (J) is the SI unit. Different fields use different units: physics (joules), nutrition (calories), electricity (watt-hours), HVAC (BTU).
Common Energy Units
- Joule (J): The SI unit. 1 J = 1 kg·m²/s².
- Calorie (cal): Energy to heat 1 gram of water by 1°C. Food calories are kilocalories.
- Watt-hour (Wh): Energy consumed by 1 watt for 1 hour. Your electricity bill uses kWh.
- BTU: British Thermal Unit. Used for heating/cooling. 1 BTU = 1,055.06 J.
Frequently Asked Questions
What is the difference between a calorie and a kilocalorie?
1 kcal = 1,000 cal. Food "Calories" (capital C) are kilocalories. When a food label says 100 Calories, it means 100 kcal.
How many joules are in a calorie?
1 cal = 4.184 joules. 1 kcal (food calorie) = 4,184 joules.
What is a BTU?
A BTU is the heat to raise 1 pound of water by 1°F. 1 BTU = 1,055.06 joules. Used in HVAC systems.
How do you convert watt-hours to joules?
Multiply watt-hours by 3,600 to get joules. 1 Wh = 3,600 J.