Convert calories to British thermal units
Converting calories to British thermal units is a common energy task, whether you are checking a recipe, a spec sheet, a travel distance or a homework problem. Since 1 cal equals 0.00396567 BTU, the math is a single multiplication — and this page does it for you instantly, with the formula, a table of common values and answers to the questions people ask most.
Exact factor
How to convert calories to British thermal units
To convert calories to British thermal units, multiply the number of calories by 0.00396567. For example, 10 cal × 0.00396567 = 0.0396567 BTU.
BTU = cal × 0.00396567
- Write down the value in calories you want to convert.
- Multiply it by 0.00396567 (the exact cal→BTU factor).
- The result is your value in British thermal units. Check it below with the converter or the table.
Conversion table
Common values of calories and their equivalents in British thermal units:
| cal | BTU |
|---|---|
| 1 | 0.00396567 |
| 2 | 0.00793133 |
| 3 | 0.011897 |
| 4 | 0.0158627 |
| 5 | 0.0198283 |
| 10 | 0.0396567 |
| 20 | 0.0793133 |
| 25 | 0.0991417 |
| 50 | 0.198283 |
| 100 | 0.396567 |
| 250 | 0.991417 |
| 500 | 1.98283 |
About these units
Calorie (cal). The small calorie is the energy needed to raise one gram of water by 1 °C, defined as exactly 4.184 joules. It is mostly used in chemistry and heat calculations.
British Thermal Unit (BTU). A British thermal unit is the energy to raise one pound of water by 1 °F, about 1,055 joules. Air conditioners, heaters and grills in the US are rated in BTU.
Frequently asked questions
How do I convert calories to British thermal units?
To convert calories to British thermal units, multiply the number of calories by 0.00396567. For example, 10 cal × 0.00396567 = 0.0396567 BTU. Or skip the math: type the value into the converter at the top of this page and the result updates instantly.
How many British thermal units are in 1 calorie?
1 cal = 0.00396567 BTU. That is the fixed relationship used by this converter and by international standards.
How many calories are in 1 british thermal unit?
1 BTU = 252.164 cal. If you are converting in the opposite direction, use our British Thermal Unit to Calorie converter for the dedicated table and FAQ.
Is the calories to British thermal units conversion exact?
Yes. Both units are defined by international agreement, so the factor of 0.00396567 is exact. Displayed results are rounded to 6 significant digits only for readability.
What is calorie used for?
The small calorie is the energy needed to raise one gram of water by 1 °C, defined as exactly 4.184 joules. It is mostly used in chemistry and heat calculations.