How to Convert Calories to Megajoules (cal 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 calories into megajoules by hand, with examples and a quick-reference table.
The conversion
To convert calories to megajoules, multiply the value by 4.184000e-06. To go the other way, divide by the same number (or multiply by 239,005.7361376673). Because the factor is tiny, scientific notation keeps the numbers manageable.
Megajoules = calories × 4.184000e-06
Worked examples
- 3 cal = 1.255200e-5 MJ
- 12.5 cal = 5.230000e-5 MJ
- 75 cal = 0.000314 MJ
Calories to Megajoules table
| Calories | Megajoules |
|---|---|
| 1 cal | 4.184000e-6 MJ |
| 2 cal | 8.368000e-6 MJ |
| 5 cal | 2.092000e-5 MJ |
| 10 cal | 4.184000e-5 MJ |
| 20 cal | 8.368000e-5 MJ |
| 25 cal | 0.000105 MJ |
| 50 cal | 0.000209 MJ |
| 100 cal | 0.000418 MJ |
| 250 cal | 0.001046 MJ |
| 500 cal | 0.002092 MJ |
| 1,000 cal | 0.004184 MJ |
Common questions
Is cal 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 Calories converter.
Mistakes to avoid
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.
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.
Background
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
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.
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
For any value, use the Calories to Megajoules Converter or browse all energy converters.
Run your own numbers: Calories to Megajoules Converter