How to Convert Calories to Joules (cal to J)
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 joules by hand, with examples and a quick-reference table.
The conversion
To convert calories to joules, multiply the value by 4.184. To go the other way, divide by the same number (or multiply by 0.2390057361). For a quick estimate, multiply by about 4.2.
Joules = calories × 4.184
Worked examples
- 3 cal = 12.552 J
- 12.5 cal = 52.3 J
- 75 cal = 313.8 J
Calories to Joules table
| Calories | Joules |
|---|---|
| 1 cal | 4.184 J |
| 2 cal | 8.368 J |
| 5 cal | 20.92 J |
| 10 cal | 41.84 J |
| 20 cal | 83.68 J |
| 25 cal | 104.6 J |
| 50 cal | 209.2 J |
| 100 cal | 418.4 J |
| 250 cal | 1,046 J |
| 500 cal | 2,092 J |
| 1,000 cal | 4,184 J |
Common questions
Is cal to J 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 Joules to Calories 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.
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.
Background
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.
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.
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 any value, use the Calories to Joules Converter or browse all energy converters.
Run your own numbers: Calories to Joules Converter