How to Convert Kilowatt-hours to Megajoules (kWh to MJ)
Energy conversions link food labels in kJ and kcal, SP Group bills in kWh and air-conditioner capacity in BTU. This guide shows how to convert kilowatt-hours into megajoules by hand, with examples and a quick-reference table.
The conversion
To convert kilowatt-hours to megajoules, multiply the value by 3.6. To go the other way, divide by the same number (or multiply by 0.2777777778). For a quick estimate, multiply by about 3.6.
Megajoules = kilowatt-hours × 3.6
Worked examples
- 3 kWh = 10.8 MJ
- 12.5 kWh = 45 MJ
- 75 kWh = 270 MJ
Kilowatt-hours to Megajoules table
| Kilowatt-hours | Megajoules |
|---|---|
| 1 kWh | 3.6 MJ |
| 2 kWh | 7.2 MJ |
| 5 kWh | 18 MJ |
| 10 kWh | 36 MJ |
| 20 kWh | 72 MJ |
| 25 kWh | 90 MJ |
| 50 kWh | 180 MJ |
| 100 kWh | 360 MJ |
| 250 kWh | 900 MJ |
| 500 kWh | 1,800 MJ |
| 1,000 kWh | 3,600 MJ |
Common questions
Is kWh to MJ exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Megajoules to Kilowatt-hours converter.
Mistakes to avoid
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Background
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
For any value, use the Kilowatt-hours to Megajoules Converter or browse all energy converters.
Run your own numbers: Kilowatt-hours to Megajoules Converter