BTU to kJ Converter
Convert British thermal units to kilojoules — the heating and cooling unit into SI. Results update as you type; exact factors shown.
One British thermal unit is 1.0551 kilojoules — see the exact factor, not a rounded rule of thumb.
How the btu to kj converter works
Energy converts through the joule. A thermochemical calorie is exactly 4.184 J, so a food Calorie (kcal) is 4.184 kJ. A kilowatt-hour is exactly 3.6 MJ. A BTU is 1,055.056 J and a US therm is 100,000 BTU.
Australia is fully metric under the National Measurement Act 1960; imperial units appear only in trade with the US and in older documents.
Common energy conversions
| From | To | Units |
|---|---|---|
| 100 BTU | 105.5056 kJ | British thermal units to kilojoules |
| 500 BTU | 527.5279 kJ | British thermal units to kilojoules |
| 1,000 BTU | 1,055.0559 kJ | British thermal units to kilojoules |
| 3,412 BTU | 3,599.8506 kJ | British thermal units to kilojoules |
| 5,000 BTU | 5,275.2793 kJ | British thermal units to kilojoules |
| 9,000 BTU | 9,495.5027 kJ | British thermal units to kilojoules |
| 12,000 BTU | 12,660.6702 kJ | British thermal units to kilojoules |
| 18,000 BTU | 18,991.0053 kJ | British thermal units to kilojoules |
| 24,000 BTU | 25,321.3405 kJ | British thermal units to kilojoules |
| 36,000 BTU | 37,982.0107 kJ | British thermal units to kilojoules |
| 50,000 BTU | 52,752.7926 kJ | British thermal units to kilojoules |
| 100,000 BTU | 105,505.5853 kJ | British thermal units to kilojoules |
Units in this converter and their exact factors
| Unit | Symbol | One unit in joules |
|---|---|---|
| joule | J | 1 joule |
| kilojoule | kJ | 1,000 joule |
| megajoule | MJ | 1,000,000 joule |
| calorie (thermochemical) | cal | 4.184 joule |
| kilocalorie (food Calorie) | kcal | 4,184 joule |
| watt-hour | Wh | 3,600 joule |
| kilowatt-hour | kWh | 3,600,000 joule |
| British thermal unit | BTU | 1,055.05585262 joule |
| therm (US) | thm | 105,505,585.262 joule |
| foot-pound | ft·lb | 1.3558179483 joule |
FAQFrequently asked questions about energy conversion
How many kJ in a BTU?
1.05506.
What is a BTU?
The heat needed to raise one pound of water by one degree Fahrenheit.
What does a 12,000 BTU air conditioner mean?
That is per hour — about 3.5 kW of cooling, which is what "one ton" of refrigeration means.
Why is it still used?
Convention in heating, ventilation and air conditioning, particularly in the US.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Measurement Institute (NMI) — Australia's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.