How to Convert Kilojoules to Megajoules (kJ 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 kilojoules into megajoules by hand, with examples and a quick-reference table.
The conversion
To convert kilojoules to megajoules, multiply the value by 0.001. To go the other way, divide by the same number (or multiply by 1,000). For a quick estimate, multiply by about 0.001.
Megajoules = kilojoules × 0.001
Worked examples
- 3 kJ = 0.003 MJ
- 12.5 kJ = 0.0125 MJ
- 75 kJ = 0.075 MJ
Kilojoules to Megajoules table
| Kilojoules | Megajoules |
|---|---|
| 1 kJ | 0.001 MJ |
| 2 kJ | 0.002 MJ |
| 5 kJ | 0.005 MJ |
| 10 kJ | 0.01 MJ |
| 20 kJ | 0.02 MJ |
| 25 kJ | 0.025 MJ |
| 50 kJ | 0.05 MJ |
| 100 kJ | 0.1 MJ |
| 250 kJ | 0.25 MJ |
| 500 kJ | 0.5 MJ |
| 1,000 kJ | 1 MJ |
Common questions
Is kJ 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 Kilojoules 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
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
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.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
For any value, use the Kilojoules to Megajoules Converter or browse all energy converters.
Run your own numbers: Kilojoules to Megajoules Converter