How to Convert Calories to British thermal units (cal to BTU)
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 british thermal units by hand, with examples and a quick-reference table.
The conversion
To convert calories to british thermal units, multiply the value by 0.0039656668. To go the other way, divide by the same number (or multiply by 252.1644000956). For a quick estimate, multiply by about 0.004.
British thermal units = calories × 0.0039656668
Worked examples
- 3 cal = 0.011897 BTU
- 12.5 cal = 0.049571 BTU
- 75 cal = 0.297425 BTU
Calories to British thermal units table
| Calories | British thermal units |
|---|---|
| 1 cal | 0.003966 BTU |
| 2 cal | 0.007931 BTU |
| 5 cal | 0.019828 BTU |
| 10 cal | 0.039657 BTU |
| 20 cal | 0.079313 BTU |
| 25 cal | 0.099142 BTU |
| 50 cal | 0.198283 BTU |
| 100 cal | 0.396567 BTU |
| 250 cal | 0.991417 BTU |
| 500 cal | 1.9828 BTU |
| 1,000 cal | 3.9657 BTU |
Common questions
Is cal to BTU 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 British thermal units to Calories converter.
Mistakes to avoid
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
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.
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.
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.
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 British thermal units Converter or browse all energy converters.
Run your own numbers: Calories to British thermal units Converter