How to Convert Calories to Kilojoules (cal to kJ)
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 kilojoules by hand, with examples and a quick-reference table.
The conversion
To convert calories to kilojoules, multiply the value by 0.004184. To go the other way, divide by the same number (or multiply by 239.0057361377). For a quick estimate, multiply by about 0.0042.
Kilojoules = calories × 0.004184
Worked examples
- 3 cal = 0.012552 kJ
- 12.5 cal = 0.0523 kJ
- 75 cal = 0.3138 kJ
Calories to Kilojoules table
| Calories | Kilojoules |
|---|---|
| 1 cal | 0.004184 kJ |
| 2 cal | 0.008368 kJ |
| 5 cal | 0.02092 kJ |
| 10 cal | 0.04184 kJ |
| 20 cal | 0.08368 kJ |
| 25 cal | 0.1046 kJ |
| 50 cal | 0.2092 kJ |
| 100 cal | 0.4184 kJ |
| 250 cal | 1.046 kJ |
| 500 cal | 2.092 kJ |
| 1,000 cal | 4.184 kJ |
Common questions
Is cal to kJ 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 Kilojoules 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.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Dropping the units
A bare number without a unit is easy to misread later. Always write the unit with the result.
Background
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
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 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 Calories to Kilojoules Converter or browse all energy converters.
Run your own numbers: Calories to Kilojoules Converter