Wh to MJ — convert watt-hours to megajoules
Exact 1 ÷ 277.777778 = 0.0036
1 watt-hour in other units
| Joules | 3,600 | J |
|---|---|---|
| Kilojoules | 3.6 | kJ |
| Megajoules | 0.0036 | MJ |
| Kilowatt-hours | 0.001 | kWh |
| Calories | 860.42065 | cal |
| Kilocalories | 0.86042065 | kcal |
| British thermal units | 3.412142 | BTU |
| Therms | 0.000034121416 | thm |
| Foot-pounds | 2,655.22 | ft·lbf |
| Electronvolts | 22,469,432,668,058,747,404,288 | eV |
Wh to MJ at a glance
| Watt-hours | Megajoules |
|---|---|
| 1 Wh | 0.0036 MJ |
| 2 Wh | 0.0072 MJ |
| 3 Wh | 0.0108 MJ |
| 5 Wh | 0.018 MJ |
| 10 Wh | 0.036 MJ |
| 20 Wh | 0.072 MJ |
| 25 Wh | 0.09 MJ |
| 50 Wh | 0.18 MJ |
| 100 Wh | 0.36 MJ |
| 250 Wh | 0.9 MJ |
| 500 Wh | 1.8 MJ |
| 1,000 Wh | 3.6 MJ |
How to convert watt-hours to megajoules
Multiply by 0.0036 — one watt-hour is 0.0036 megajoules. That factor is exact: it comes from the definition of the units rather than from a measurement, so it will not change and does not need rounding.
Working 1 ÷ 277.777778 = 0.0036
Questions
How many megajoules are in a watt-hour?
One watt-hour is 0.0036 megajoules. This figure is exact — it comes from the definition of the unit, not a measurement.
What is 1 watt-hour in megajoules?
1 watt-hour is 0.0036 megajoules. The working is 1 ÷ 277.777778 = 0.0036.
Is a food Calorie the same as a calorie?
No — it is a thousand of them. The Calorie on a nutrition label is a kilocalorie, written with a capital C in principle and almost never in practice. A 250 Calorie chocolate bar holds 250,000 physics calories, or about 1,046 kilojoules, which is why European labels quote kJ alongside.
What does a kilowatt-hour actually represent?
One kilowatt drawn for one hour — a 1,000 W heater running for sixty minutes, or a 100 W bulb for ten hours. It is the unit your electricity bill is priced in, and it equals exactly 3.6 million joules.
How much energy is one BTU?
Roughly the heat needed to raise one pound of water by one degree Fahrenheit — about 1,055 joules, or the energy in a single kitchen match. Air conditioners are rated in BTU per hour, where a 12,000 BTU/h unit is one "ton" of cooling and draws around 3.5 kW of heat.
Why is the electronvolt so small?
Because it is sized for single particles: it is the energy one electron picks up crossing a one-volt potential difference. At about 1.6 × 10⁻¹⁹ joules it would be absurd for anything larger, which is precisely why particle physics uses it instead of dragging around twenty leading zeros.