Calories to BTU Converter

One calorie (small) equals 0.0039656668 british thermal units (BTU). To convert calorie (small)s to british thermal units, multiply by 0.0039656668; to go back the other way, multiply by 252.1644 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 calorie (small)s and british thermal units actually measure

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.

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.

Calories to BTU conversion table

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

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

Multiply the number of calorie (small)s by 0.0039656668.

For example, 25 cal × 0.0039656668 = 0.099141671 BTU.

Going the other way, divide by 0.0039656668 — or multiply by 252.1644, 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.