Energy Converter
Convert between energy units including Joule (J), Kilojoule (kJ), Calorie (cal), Kilocalorie (kcal), Kilowatt-hour (kWh), BTU, and more.
Energy Converter
Convert between energy units. All conversions use joule (J) as the base SI unit.
Result
Enter a value and click "Convert" to see the result
Understanding Energy Units
Energy is the capacity to do work. The SI unit of energy is the Joule (J), but many other units are used across different fields including nutrition, electricity, and engineering.
Common Energy Units:
- Joule (J): SI base unit of energy — 1 J = 1 kg·m²/s²
- Kilojoule (kJ): 1,000 joules — used in food energy labeling outside the US
- Calorie (cal): Energy to raise 1 g of water by 1°C — used in chemistry
- Kilocalorie (kcal): 1,000 calories — the “food calorie” used in nutrition
- Kilowatt-hour (kWh): Energy unit used for electricity billing, 1 kWh = 3,600,000 J
- BTU: British Thermal Unit — used in HVAC and heating systems in the US
Key Conversions:
- 1 kcal = 4,184 J = 4.184 kJ
- 1 kWh = 3,600,000 J = 3,600 kJ = 860 kcal
- 1 BTU = 1,055 J ≈ 0.252 kcal
- 1 kJ = 0.239 kcal
Frequently Asked Questions
How do I convert joules to calories?
Divide joules by 4.184 to get calories. One food Calorie (kcal) equals 4,184 joules.
How many joules are in a kilowatt-hour?
1 kWh = 3,600,000 joules (3.6 million). It represents using 1,000 watts for one hour, the unit on your electricity bill.
What is the difference between a calorie and a Calorie?
A small calorie (cal) is the energy to heat 1 gram of water by 1°C. A food Calorie (kcal, capital C) is 1,000 small calories. Nutrition labels use kcal.
What units measure energy?
Common energy units include the joule (J), calorie (cal), kilowatt-hour (kWh), British thermal unit (BTU), and electronvolt (eV). This tool converts between them.