How to Convert Joules to Calories (J to cal)
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 joules into calories by hand, with examples and a quick-reference table.
The conversion
To convert joules to calories, multiply the value by 0.2390057361. To go the other way, divide by the same number (or multiply by 4.184). For a quick estimate, multiply by about 0.24.
Calories = joules × 0.2390057361
Worked examples
- 3 J = 0.717017 cal
- 12.5 J = 2.9876 cal
- 75 J = 17.9254 cal
Joules to Calories table
| Joules | Calories |
|---|---|
| 1 J | 0.239006 cal |
| 2 J | 0.478011 cal |
| 5 J | 1.195 cal |
| 10 J | 2.3901 cal |
| 20 J | 4.7801 cal |
| 25 J | 5.9751 cal |
| 50 J | 11.9503 cal |
| 100 J | 23.9006 cal |
| 250 J | 59.7514 cal |
| 500 J | 119.5029 cal |
| 1,000 J | 239.0057 cal |
Common questions
Is J to cal 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 Calories to Joules 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.
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.
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 Joules to Calories Converter or browse all energy converters.
Run your own numbers: Joules to Calories Converter