This converter turns British thermal units into kilocalories instantly, using the exact factor 1 British thermal unit = 0.2521644007 kilocalories. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
The heat to raise one pound of water by one degree Fahrenheit; standard for HVAC. The dietary Calorie shown on US nutrition labels.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
British thermal units- The amount you are converting, measured in British thermal units
0.2521644007- The exact number of kilocalories in one British thermal unit
kilocalories- The converted result
How it works, step by step
- Enter the number of British thermal units you want to convert.
- The value is multiplied by 0.2521644007, the exact conversion factor.
- The result is displayed in kilocalories, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 British thermal units
Multiply 5 by 0.2521644. That gives 1.2608 kilocalories. A quick sanity check: one British thermal unit is smaller than one kilocalorie, so the number should get smaller — and it does.
Converting 72 British thermal units
72 × 0.2521644 = 18.1558 kilocalories. Working backwards, 18.1558 ÷ 0.2521644 returns 72 British thermal units, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many kilocalories are in one British thermal unit?
Exactly 0.2521644007. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert British thermal units to kilocalories?
Kilocalories = British thermal units × 0.2521644007. To reverse it, divide instead: British thermal units = kilocalories ÷ 0.2521644007, which is the same as multiplying by 3.965666831.
Is the British thermal unit bigger than the kilocalorie?
No. One British thermal unit is only 0.252164 of a kilocalorie, so the kilocalorie is the larger unit.
Why does my answer differ slightly from other btu to kilocalories converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a British thermal unit?
The heat to raise one pound of water by one degree Fahrenheit; standard for HVAC.
What is a kilocalorie?
The dietary Calorie shown on US nutrition labels.
British Thermal Units to kilocalories reference table
| British Thermal Units | Kilocalories |
|---|---|
| 0.5 BTU | 0.126082 kcal |
| 1 BTU | 0.252164 kcal |
| 2 BTU | 0.504329 kcal |
| 3 BTU | 0.756493 kcal |
| 5 BTU | 1.2608 kcal |
| 10 BTU | 2.5216 kcal |
| 15 BTU | 3.7825 kcal |
| 20 BTU | 5.0433 kcal |
| 25 BTU | 6.3041 kcal |
| 50 BTU | 12.6082 kcal |
| 75 BTU | 18.9123 kcal |
| 100 BTU | 25.2164 kcal |
| 250 BTU | 63.0411 kcal |
| 500 BTU | 126.0822 kcal |
| 1000 BTU | 252.1644 kcal |
Exact factor: 1 British thermal unit = 0.2521644007 kilocalories. Values rounded for display.