Calories to British thermal units
Type a value in calories to see it in British thermal units straight away, or type in the second box to convert back.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Type the value in the calories box.
- Read the result in British thermal units as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
BTU = cal × 0.003965666831
Multiply the value in calories by 0.003965666831 to get British thermal units.
Example
To convert 25 cal to British thermal units: 25 × 0.003965666831 = 0.0991417 BTU.
Conversion table
| Calories (cal) | British thermal units (BTU) |
|---|---|
| 1 | 0.00396567 |
| 2 | 0.00793133 |
| 3 | 0.011897 |
| 5 | 0.0198283 |
| 10 | 0.0396567 |
| 20 | 0.0793133 |
| 25 | 0.0991417 |
| 50 | 0.198283 |
| 100 | 0.396567 |
| 250 | 0.991417 |
| 500 | 1.98283 |
| 1,000 | 3.96567 |
About the units
- Calorie
- The small calorie in its thermochemical definition, exactly 4.184 joules. The food calorie on labels equals 1000 of these.
- British thermal unit
- The imperial unit of heat, using the International Table definition of exactly 1055.05585262 joules. Seen in air conditioner and heater ratings.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many British thermal units are in one calorie?
1 cal = 0.00396567 BTU exactly.
How do I convert calories to British thermal units?
Use BTU = cal × 0.003965666831. For example, 25 cal = 0.0991417 BTU.
How many calories are in one British thermal unit?
1 BTU = 252.164 cal.
Which calorie do these converters use?
The thermochemical calorie, exactly 4.184 joules, the factor many countries use to turn kcal into kJ on food labels. The International Table calorie is 4.1868 joules, less than 0.07% larger.
What is the difference between kW and kWh?
A kilowatt is a unit of power, the rate of using energy, while a kilowatt-hour is an amount of energy. A 2 kW heater running for three hours uses 6 kWh.