BTU to Calories Converter

One british thermal unit equals 252.1644 calorie (small)s (cal). To convert british thermal units to calorie (small)s, multiply by 252.1644; to go back the other way, multiply by 0.0039656668 instead.

The converter above does it as you type and shows the working underneath, so you can check the arithmetic rather than take the number on trust.

What british thermal units and calorie (small)s actually measure

British thermal unit (BTU) — A British thermal unit raises a pound of water by one degree Fahrenheit — about 1,055 joules. Heating, air conditioning and gas in the US.

Calorie (small) (cal) — A calorie raises one gram of water by one degree Celsius — 4.184 joules. Chemistry and physics. Note this is the small calorie, not the food one.

BTU to Calories conversion table

The most common values, worked out in advance. Anything not listed can be typed straight into the converter.

How to convert british thermal units to calorie (small)s by hand

Multiply the number of british thermal units by 252.1644.

For example, 25 BTU × 252.1644 = 6304.11 cal.

Going the other way, divide by 252.1644 — or multiply by 0.0039656668, which is the same thing and easier to do in your head.

Everything runs in your browser

There is no server involved in the calculation. The numbers you type never leave your device, nothing is logged, and the page keeps working with no connection once it has loaded. That is not a marketing line — it is simply how the tool is built, because a calculation like this has no reason to touch a network.