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Energy
Kilojoules to Watt-hours
Convert kilojoules (kJ) to watt-hours (Wh). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 kJ = 0.277778 Wh
Kilojoules to Watt-hours Conversion Table
Common values, ready to copy:
| kilojoules | watt-hours |
|---|---|
| 1 kJ | 0.277778 Wh |
| 2 kJ | 0.555556 Wh |
| 5 kJ | 1.3889 Wh |
| 10 kJ | 2.7778 Wh |
| 25 kJ | 6.9444 Wh |
| 50 kJ | 13.8889 Wh |
| 100 kJ | 27.7778 Wh |
| 1,000 kJ | 277.78 Wh |
Formula
watt-hours = kilojoules × 2.77777778e-1
Energy uses the SI joule. Food calories (kcal) are 1,000 small calories: 1 kcal = 4,184 J. 1 kWh = 3.6 MJ = 3,600,000 J. 1 BTU = 1,055.06 J.
About Kilojoules and Watt-hours
Kilojoules (kJ): A thousand joules; the practical SI energy unit for food and nutrition in metric countries. Common uses: Food energy labeling outside the US, electrical energy in kJ for small batteries, and biology (metabolism).
Watt-hours (Wh): The energy consumed by a 1-watt device in 1 hour; equals 3,600 joules. Common uses: Small battery capacities (laptop batteries are typically 40-100 Wh), and lighting energy use.
How the conversion works
Energy uses the SI joule. Food calories (kcal) are 1,000 small calories: 1 kcal = 4,184 J. 1 kWh = 3.6 MJ = 3,600,000 J. 1 BTU = 1,055.06 J.
The exact relationship is watt-hours = kilojoules × 2.77777778e-1, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.
When this conversion matters
Converting between kilojoules and watt-hours comes up wherever energy measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.