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Energy
Megajoules to Watt-hours
Convert megajoules (MJ) to watt-hours (Wh). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 MJ = 277.78 Wh
Megajoules to Watt-hours Conversion Table
Common values, ready to copy:
| megajoules | watt-hours |
|---|---|
| 1 MJ | 277.78 Wh |
| 2 MJ | 555.56 Wh |
| 5 MJ | 1388.89 Wh |
| 10 MJ | 2777.78 Wh |
| 25 MJ | 6944.44 Wh |
| 50 MJ | 13888.89 Wh |
| 100 MJ | 27777.78 Wh |
| 1,000 MJ | 277777.78 Wh |
Formula
watt-hours = megajoules × 2.77777778e+2
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 Megajoules and Watt-hours
Megajoules (MJ): A million joules; the unit for larger-scale energy quantities. Common uses: Daily food intake (a typical adult consumes 8-10 MJ per day), fuel energy content (gasoline ≈ 34 MJ per liter), and industrial energy.
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 = megajoules × 2.77777778e+2, 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 megajoules 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.