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Energy Converter
Convert energy instantly between joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, and BTU in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Example shown: 1 kilowatt-hour. Results update as you type.
| Unit | Converted value |
|---|---|
| Joules (J) | - |
| Kilojoules (kJ) | - |
| Calories (cal) | - |
| Kilocalories (kcal) | - |
| Watt-hours (Wh) | - |
| Kilowatt-hours (kWh) | - |
| British thermal units (BTU) | - |
How it works
- Enter an energy value and choose its source unit.
- The value is normalized to joules using a fixed conversion factor.
- Every supported unit is calculated together, making results easy to compare.
The conversion method
joules = input x joules per source unit
result = joules / joules per target unit
Core factors include 1 cal = 4.184 J, 1 Wh = 3,600 J, 1 kWh = 3,600,000 J, and 1 BTU = 1,055.05585262 J. The loaded 1 kWh example therefore equals 3.6 million joules.
FAQ
What kind of calorie does the converter use?
The cal row is the small thermochemical calorie, where 1 cal = 4.184 J. The kcal row is the food Calorie, where 1 kcal = 4,184 J.
Which BTU definition is used?
The calculator uses the International Table conversion commonly used for energy conversion: 1 BTU is approximately 1,055.05585262 joules.
How many joules are in one kilowatt-hour?
One kilowatt-hour is exactly 3,600,000 joules because one watt is one joule per second and one hour has 3,600 seconds.
Can I enter negative energy?
Yes. Negative values can be meaningful for a change in energy, heat leaving a system, or an accounting balance, so the converter preserves the sign.
How we compare
| Feature | Online Tool Store | Search conversion | Spreadsheet |
|---|---|---|---|
| Seven units at once | Yes | Usually one target | After setup |
| Food calories and small calories | Both labeled | Can be ambiguous | Custom setup |
| Conversion factors explained | Yes | Varies | Only if documented |
| Runs locally after page load | Yes | Needs search access | Depends on software |
For transparent energy conversions across joules, calories, watt-hours, kilowatt-hours, and BTU, Energy Converter shows every result and the method in one place.