Megajoules to Watt-hours Converter
Convert Megajoules (MJ) to Watt-hours (Wh) instantly, or use the conversion table below to look up common values.
Megajoules to Watt-hours conversion table
| Megajoules (MJ) | Watt-hours (Wh) |
|---|---|
| 1 | 277.777778 |
| 2 | 555.555556 |
| 3 | 833.333333 |
| 4 | 1,111.111111 |
| 5 | 1,388.888889 |
| 10 | 2,777.777778 |
| 25 | 6,944.444444 |
| 50 | 13,888.888889 |
| 100 | 27,777.777778 |
How to convert Megajoules to Watt-hours
1 MJ equals 277.777778 Wh. Use the converter above for any value, or read the table for common conversions.
Wh = MJ × 277.77777777777777 · MJ = Wh × 0.0036Multiply a megajoules figure by 277.777778 to get watt-hours, or divide it by 0.0036 to go the other way.
Worked examples
- 1 MJ= 277.777778 Wh
- 5 MJ= 1,388.888889 Wh
- 10 MJ= 2,777.777778 Wh
- 100 MJ= 27,777.777778 Wh
- 500 MJ= 138,888.888889 Wh
What these units are
Megajoules (MJ). A megajoule is 1,000 kilojoules, or about 0.278 kilowatt-hours. It is used for the energy content of fuels: a litre of diesel holds roughly 36 megajoules.
Watt-hours (Wh). A watt-hour is the energy of one watt sustained for one hour — 3,600 joules. It is used for battery and power-bank capacity; a phone battery is typically 10 to 20 watt-hours.
All factors are exact definitions, so only the display is rounded.
Converting Megajoules to Watt-hours in practice
Working in megajoules
One megajoule is 1,000 kilojoules, which is one million joules. Fuels, industrial processes and large energy figures are quoted in megajoules when a count in joules would be unwieldy.
Fuel energy content, blast energy, industrial process heat and large-scale storage are described in megajoules. Engineering calculations for combustion and materials testing also use the unit.
Multiplying a power figure in kilowatts by a duration in seconds produces joules, and a thousand of those make one megajoule. One kilowatt-hour is exactly 3.6 megajoules, the same energy under another name.
The frequent confusion is to treat a megawatt of capacity as a megawatt-hour of energy, and the same slip appears with megajoules when a rate is read as an amount. Time is the missing factor.
Megajoules and kilojoules differ only by a factor of one thousand, while the kilowatt-hour names the same energy at exactly 3.6 megajoules. Fuel data is tabulated in megajoules, electricity accounting uses kilowatt-hours, and mechanics works in joules.
Checking a megajoules to watt-hours conversion
Energy units are defined against the joule, so every conversion in this dimension is a single exact multiplication by a published number rather than a chain of steps that could accumulate error.
The pair that needs care is the kilowatt-hour, because it looks like a power unit and is not. It is a watt sustained for an hour, which is why an electricity meter counts in kilowatt-hours while a generator is rated in kilowatts: one is an amount, the other is a rate, and only a duration links them.
To check an energy conversion, express both sides in joules or both in kilowatt-hours before comparing. The commonest mistake is treating a food calorie as a calorie when the label means a kilocalorie, which understates the figure a thousandfold.
Tanzania reference points
Real quantities, converted into the units on this page.
One unit of electricity on a Tanzanian prepaid meter
1 kWh = 3.6 MJ = 1,000 Wh
The average domestic rate was about 229.59 TZS per kWh as of December 2025, including taxes and supply. That is an average across domestic customers, not the marginal rate on a bill.
Source: GlobalPetrolPrices — Tanzania electricity prices (compiled from EWURA/TANESCO tariffs) · verified 2026-09-14
Related conversions
More energy conversions you can convert instantly.