Convert BTU to kilojoule.

Convert BTU (BTU) to kilojoule (kJ). This is a fixed-ratio conversion — multiply the input by the factor below.

Formula

kJ = BTU × 1.05506

Reference values

Things to watch for

• The 'calorie' in nutrition labels is actually a kilocalorie (kcal, sometimes Cal with capital C). A '200 calorie' candy bar is 200 kcal = 836 kJ.
• 1 kWh = 3.6 MJ (exactly). Used for billing electricity.
• Electron-volts (eV) are convenient at atomic/molecular scales; joules at human scales; kWh at building scales.

What is a British thermal unit?

One BTU equals about 1,055.06 joules — the energy to raise one pound of water by 1°F. HVAC (air conditioner ratings, e.g. 12,000 BTU/h = 1 ton), natural gas heating, and US heating equipment.

What is a kilojoule?

One kilojoule equals exactly 1,000 joules. Food energy labels in Europe and Australia (an apple is about 200 kJ), thermal calculations.

What does BTU look like in everyday objects?

Concrete examples often help when a unit doesn't have an intuitive feel. 1 BTU is the energy to heat 1 lb of water by 1°F; 1000 BTU is about a slice of pizza.

How to convert British thermal unit to kilojoule

To convert a value from British thermal unit (BTU) to kilojoule (kJ), apply the conversion factor shown in the formula above. The calculation is the same whether you do it by hand, in a spreadsheet, or with the live converter on this page.

Steps:

1. Take your input value in BTU.
2. Apply the formula kJ = BTU × 1.05506.
3. The result is your value in kJ.

For repeated calculations, save the formula in a spreadsheet or use the live converter at the top of this page — it handles the math automatically and displays the result as you type.

Frequently asked questions

How do I convert BTU to kJ?

Apply the formula BTU → kJ shown above, or just type your value into the converter at the top of this page. The result updates instantly.

Which is bigger, BTU or kJ?

This depends on the conversion ratio in the formula. If the factor multiplied by your value gives a larger number, then kJ is the smaller unit (so it takes more of them to express the same quantity). If the result is smaller, then kJ is the larger unit.

When would I use BTU versus kJ?

Both units measure energy, so the choice depends on context. British thermal unit is typically used for food labeling, batteries, fuel, and electric utility billing; kilojoule similarly. Most professional fields standardize on one or the other based on regional conventions or technical tradition.

How precise is this BTU to kJ conversion?

The conversion factor shown is the internationally defined exact value (or the best-published approximation if the relationship is irrational, like degrees-to-radians). The live converter on this page uses double-precision floating-point math, accurate to about 15 significant digits — far beyond any practical engineering need.

Is the conversion ratio exact, or an approximation?

Most unit conversions between SI metric units, and between SI and US customary units, have been formally defined as exact values since the 1959 international yard-pound agreement and subsequent SI redefinitions. Exceptions are unit pairs that involve irrational numbers (radians, e.g.) or empirical conversions (like food calories, which depend on temperature). When in doubt, consult the formula at the top of this page.

Related conversions

See also