BTU to Kilocalories
Convert btu (BTU) to kilocalories (kcal). Both measure work and power, and the conversion comes up in nutrition, electricity, fitness work.
The Formula
``
kilocalories = btu × 0.252164400722
btu = kilocalories × 3.96566683139
`
One BTU is 0.252164 kilocalories, and one kilocalory is 3.9657 btu.
Conversion Table
| BTU | Kilocalories |
|---|---|
| 1 BTU | 0.252164 kcal |
| 2 BTU | 0.504329 kcal |
| 5 BTU | 1.2608 kcal |
| 10 BTU | 2.5216 kcal |
| 25 BTU | 6.3041 kcal |
| 50 BTU | 12.6082 kcal |
| 100 BTU | 25.2164 kcal |
| 500 BTU | 126.0822 kcal |
| 1,000 BTU | 252.1644 kcal |
The Other Direction
| Kilocalories | BTU |
|---|---|
| 1 kcal | 3.9657 BTU |
| 2 kcal | 7.9313 BTU |
| 5 kcal | 19.8283 BTU |
| 10 kcal | 39.6567 BTU |
| 25 kcal | 99.1417 BTU |
| 50 kcal | 198.2833 BTU |
| 100 kcal | 396.5667 BTU |
| 500 kcal | 1,982.83 BTU |
| 1,000 kcal | 3,965.67 BTU |
What Each Unit Is
BTU (BTU) — the energy to raise one pound of water by one degree Fahrenheit, or 1,055 joules. The imperial thermal unit, still standard for US heating, cooling and gas.
Kilocalories (kcal) — 1,000 small calories, or 4,184 joules — the "Calorie" on a nutrition label. Capitalised as Calorie to distinguish it, a convention almost nobody follows.
A Sense of Scale
A window air conditioner is 5,000–12,000 BTU/h- US furnaces are rated in BTU
- An apple is 95 kcal
- Daily intake is about 2,000 kcal
- A marathon burns roughly 2,600 kcal
Doing It in Your Head
Divide by 4. That is off by 0.86% — close enough to judge a
distance, a weight or a price, and not close enough to sign off on a drawing.
Exact Mental shortcut 2.5216 kcal 2.5 kcal 25.2164 kcal 25 kcal
Precision
The factor 0.252164400722 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.
In Code
`javascript
const btuToKilocalorie = (value) => value * 0.252164400722;
``
Where This Conversion Comes Up
- Nutrition
- Electricity
- Fitness
- Heating
- Fuel
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 BTU with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 BTU becomes | Error |
|---|---|---|---|
| 0 | 0 | 0 | 100.0000% |
| 1 | 0.3 | 41.1 | 18.9700% |
| 2 | 0.25 | 34.25 | 0.8583% |
| 3 | 0.252 | 34.524 | 0.0652% |
| 4 | 0.2522 | 34.5514 | 0.0141% |
The right number of significant figures is set by your input, not by the converter. If you measured btu to three significant figures, the answer in kilocalories is only good to three — writing more digits claims precision the measurement never had.