Convert BTU to Kilojoules

About converting BTU to Kilojoules

BTU (BTU) and Kilojoules (kJ) are both units of energy, so converting between them is a single multiplication: multiply your BTU figure by 1.0551. Ten BTU comes to 10.5506 Kilojoules, and a hundred works out at 105.5056 Kilojoules.

Rule of thumb: going from BTU to Kilojoules multiplies, so the figure always grows — one BTU is already 1.0551 Kilojoules. If your answer came out smaller, you have the conversion the wrong way round.

What is a BTU?

The BTU is the heat needed to raise one pound of water by one degree Fahrenheit — and there is no single BTU. Water takes slightly different amounts of heat to warm depending on the temperature it starts from, so several definitions exist (thermochemical, International Table, 39 °F, 59 °F, 60 °F and others), differing from one another by a fraction of a percent. This converter uses one common value, so treat the result as convention-dependent rather than absolute. In the US it is the unit of heating and cooling capacity, though air conditioners are really rated in BTU per hour and the "per hour" is routinely dropped in marketing.

What is a Kilojoule?

A kilojoule is a thousand joules, the size at which the joule becomes practical for everyday quantities. In Australia and New Zealand it is the primary unit on nutrition labels — food energy is quoted in kilojoules first, with calories relegated to a secondary figure or dropped entirely — so shoppers there think about daily intake in thousands of kilojoules rather than thousands of calories. It is also the working unit of chemistry, where reaction and bond energies are tabulated per mole. European labels print both kJ and kcal, which is why the same packet carries two different numbers for the same food.

To put both in perspective: a wooden kitchen match releases roughly one BTU, while a slice of bread carries roughly 300 kilojoules.

The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Kilojoules to BTU converter, or browse all Energy converters.