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Energy
BTU to Kilojoules
Convert BTU (BTU) to kilojoules (kJ). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 BTU = 1.0551 kJ
BTU to Kilojoules Conversion Table
Common values, ready to copy:
| BTU | kilojoules |
|---|---|
| 1 BTU | 1.0551 kJ |
| 2 BTU | 2.1101 kJ |
| 5 BTU | 5.2753 kJ |
| 10 BTU | 10.5506 kJ |
| 25 BTU | 26.3765 kJ |
| 50 BTU | 52.753 kJ |
| 100 BTU | 105.51 kJ |
| 1,000 BTU | 1055.06 kJ |
Formula
kilojoules = BTU × 1.05506000e+0
Energy uses the SI joule. Food calories (kcal) are 1,000 small calories: 1 kcal = 4,184 J. 1 kWh = 3.6 MJ = 3,600,000 J. 1 BTU = 1,055.06 J.
About BTU and Kilojoules
BTU (BTU): British Thermal Unit; the energy to raise one pound of water by one degree Fahrenheit; defined as exactly 1,055.06 J. Common uses: US heating and air conditioning (a 24,000 BTU air conditioner cools roughly a 1,500 sq ft room), and US natural gas billing.
Kilojoules (kJ): A thousand joules; the practical SI energy unit for food and nutrition in metric countries. Common uses: Food energy labeling outside the US, electrical energy in kJ for small batteries, and biology (metabolism).
How the conversion works
Energy uses the SI joule. Food calories (kcal) are 1,000 small calories: 1 kcal = 4,184 J. 1 kWh = 3.6 MJ = 3,600,000 J. 1 BTU = 1,055.06 J.
The exact relationship is kilojoules = BTU × 1.05506000e+0, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.
When this conversion matters
Converting between BTU and kilojoules comes up wherever energy measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.