How do I convert joules, calories, kWh, BTU?
Energy units converter: joule (J), kilojoule (kJ), calorie (cal), kilocalorie (kcal), watt-hour (Wh), kilowatt-hour (kWh), megawatt-hour (MWh), BTU, electronvolt (eV), foot-pound (ft·lb), erg, therm.
Type a value in one unit, see all the others live.
Perfect for electricity bills (kWh ↔ J), diet and cooking (kcal ↔ kJ on labels), air conditioning (BTU ↔ kW), physics (J ↔ eV ↔ erg).
Everything computed locally, no data sent.
How to use it
- Type a value on the left and pick the source unit.
- On the right you see all other units live: kJ, kcal, kWh, BTU, eV etc.
- Click any result = copies the value to clipboard.
- Works both ways. Change the source unit and the value re-converts automatically.
When this is useful
The most common uses:
- Electricity bills. Utility bills in kWh, but how many joules is that? 1 kWh = 3,600,000 J.
- Diet and cooking. Food labels show kcal and kJ. 1 kcal = 4.184 kJ. Convert at a glance.
- Air conditioning. AC units rated in BTU/h. 12,000 BTU/h = 3.5 kW. Helps pick the right unit for a room.
- Heating. Therm used in US and UK gas bills. 1 therm ≈ 100,000 BTU.
- Physics and chemistry. eV for particle energy (1 eV = 1.6×10⁻¹⁹ J), erg in classical mechanics (1 J = 10⁷ erg).
- Engineering. ft·lb in imperial mechanics (1 ft·lb ≈ 1.356 J).
Questions and answers
1 kWh = 3,600,000 J (3.6 MJ). From the definition. Kilowatt × hour = 1000 W × 3600 s = 3,600,000 W·s = 3,600,000 J.