British Thermal Units to Kilojoules
Convert British thermal units to kilojoules instantly — one British thermal unit is 1.05506 kilojoules.
| British Thermal Units | Kilojoules |
|---|---|
| 1 BTU | 1.055056 kJ |
| 2 BTU | 2.110112 kJ |
| 3 BTU | 3.165168 kJ |
| 5 BTU | 5.275279 kJ |
| 10 BTU | 10.550559 kJ |
| 25 BTU | 26.376396 kJ |
| 50 BTU | 52.752793 kJ |
| 100 BTU | 105.505585 kJ |
How to use
- Enter a value in the British Thermal Units field.
- The Kilojoules figure appears immediately — no button to press.
- Typing in the Kilojoules field converts back to British Thermal Units the same way.
- Use the reference table for the values that come up most often.
British Thermal Units to Kilojoules formula
Converting British thermal units to kilojoules is a single multiplication by 1.05505585.
kJ = BTU × 1.05505585
Why this factor: the British thermal unit and the kilojoule are both defined against the joule, so dividing one definition by the other gives 1.05505585 directly. Both definitions are set out in full below.
To go the other way, divide by 1.05505585 — or use the Kilojoules to British Thermal Units converter, which is the same calculation reversed.
Worked example
Start with 500 BTU. Multiply by 1.05505585 to get 527.527926 kJ.
500 BTU × 1.05505585 = 527.527926 kJ
The converter above does this for any value you type, in either direction.
What is a British thermal unit?
A BTU is the energy needed to raise one pound of water by one degree Fahrenheit.
Definition: The international-table BTU is about 1,055.056 joules.
Where it is used: US heating and air-conditioning capacity ratings, natural gas pricing, and boiler output.
Worth knowing: Air-conditioner ratings quoted as 'BTU' are really BTU per hour — a rate of cooling, not a quantity of energy.
What is a kilojoule?
A kilojoule is 1,000 joules, the metric unit of food energy.
Definition: Exactly 1,000 joules.
Where it is used: Nutrition labels in Europe and Australia, and heating and cooling loads.
British Thermal Units vs Kilojoules
The British thermal unit is a US customary unit while the kilojoule is a metric unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many kilojoules are in a British thermal unit?
One British thermal unit equals 1.05505585 kilojoules.
What is the formula to convert British thermal units to kilojoules?
Multiply the number of British thermal units by 1.05505585. To reverse it, divide by 1.05505585 instead.
How do I convert kilojoules back to British thermal units?
Divide by 1.05505585, which is the same as multiplying by 0.94781712.
How many kilojoules are in 10 British thermal units?
10 BTU works out to 10.550559 kJ.
Is there anything to watch out for with British thermal units?
Air-conditioner ratings quoted as 'BTU' are really BTU per hour — a rate of cooling, not a quantity of energy.
How is the British thermal unit defined?
The international-table BTU is about 1,055.056 joules.