How to convert calories to British thermal units
BTU = cal × 0.003965666831Multiply the value in calories by 0.003965666831. To go the other way, multiply by 252.1644007 (or divide by 0.003965666831).
A calorie is smaller than a British thermal unit: it takes 252.1644007 calories to make one British thermal unit.
Worked examples
- 1 calorie (thermochemical)1 cal × 0.003965666831 = 0.003965666831 BTU
- 5 calories5 cal × 0.003965666831 = 0.01982833416 BTU
- 10 calories10 cal × 0.003965666831 = 0.03965666831 BTU
- 20 calories20 cal × 0.003965666831 = 0.07931333663 BTU
- 100 calories100 cal × 0.003965666831 = 0.3965666831 BTU
Calories to British thermal units conversion table
Values are calculated by the conversion engine and rounded to 8 significant figures.
| Calories (cal) | British thermal units (BTU) |
|---|---|
| 0.1 cal | 0.00039656668 BTU |
| 0.25 cal | 0.00099141671 BTU |
| 0.5 cal | 0.0019828334 BTU |
| 1 cal | 0.0039656668 BTU |
| 2 cal | 0.0079313337 BTU |
| 3 cal | 0.011897 BTU |
| 4 cal | 0.015862667 BTU |
| 5 cal | 0.019828334 BTU |
| 6 cal | 0.023794001 BTU |
| 7 cal | 0.027759668 BTU |
| 8 cal | 0.031725335 BTU |
| 9 cal | 0.035691001 BTU |
| 10 cal | 0.039656668 BTU |
| Calories (cal) | British thermal units (BTU) |
|---|---|
| 12 cal | 0.047588002 BTU |
| 15 cal | 0.059485002 BTU |
| 20 cal | 0.079313337 BTU |
| 25 cal | 0.099141671 BTU |
| 30 cal | 0.11897 BTU |
| 40 cal | 0.15862667 BTU |
| 50 cal | 0.19828334 BTU |
| 75 cal | 0.29742501 BTU |
| 100 cal | 0.39656668 BTU |
| 250 cal | 0.99141671 BTU |
| 500 cal | 1.9828334 BTU |
| 1,000 cal | 3.9656668 BTU |
About the units
Calorie (cal)
The “small” calorie: exactly 4.184 J (thermochemical definition), roughly the energy to heat one gram of water by 1 °C.
British thermal unit (BTU)
The International Table BTU, 1,055.05585262 J — roughly the energy to heat one pound of water by 1 °F. Furnace and AC capacities are rated in BTU (per hour). One British thermal unit equals 1,055.055853 joules (J).
Frequently asked questions
How many British thermal units are in one calorie?
There are 0.003965666831 British thermal units in one calorie, and this value is exact by definition.
How do I convert calories to British thermal units?
Multiply the number of calories by 0.003965666831. For example, 10 cal × 0.003965666831 = 0.03965666831 BTU.
How many calories are in one British thermal unit?
One British thermal unit equals 252.1644007 calories. That is the reverse factor, 1 ÷ 0.003965666831.
What is 10 calories in British thermal units?
10 cal = 0.03965666831 BTU.
Is this cal to BTU converter accurate?
Yes. Both units are defined exactly in terms of SI units, so the conversion factor is exact; results are shown to 12 significant figures by default and you can change precision in the converter. Calculations run in your browser using the same tested engine that generated this page.