British Thermal Units to Joules
Type a value in either box to convert between British thermal units and joules. The factor is 1055.06.
| British Thermal Units | Joules |
|---|---|
| 1 BTU | 1055.055853 J |
| 2 BTU | 2110.111705 J |
| 3 BTU | 3165.167558 J |
| 5 BTU | 5275.279263 J |
| 10 BTU | 10550.558526 J |
| 25 BTU | 26376.396315 J |
| 50 BTU | 52752.792631 J |
| 100 BTU | 105505.585262 J |
How to use
- Enter a value in the British Thermal Units field.
- The Joules figure appears immediately — no button to press.
- Typing in the Joules 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 Joules formula
To convert British thermal units to joules, multiply by 1055.05585.
J = BTU × 1055.05585
Why this factor: the British thermal unit and the joule are both defined against the joule, so dividing one definition by the other gives 1055.05585 directly. Both definitions are set out in full below.
To go the other way, divide by 1055.05585 — or use the Joules to British Thermal Units converter, which is the same calculation reversed.
Worked example
Given 100 BTU, multiplying by 1055.05585 yields 105505.585262 J.
100 BTU × 1055.05585 = 105505.585262 J
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 joule?
The joule is the SI unit of energy — the work done by one newton acting over one meter.
Definition: Defined as 1 N·m, equivalently one watt-second. Named after James Prescott Joule.
Where it is used: All scientific energy calculations, food energy on European labels, and mechanical work.
British Thermal Units vs Joules
The British thermal unit is a US customary unit while the joule is an SI 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 joules are in a British thermal unit?
One British thermal unit equals 1055.05585 joules.
What is the formula to convert British thermal units to joules?
Multiply the number of British thermal units by 1055.05585. To reverse it, divide by 1055.05585 instead.
How do I convert joules back to British thermal units?
Divide by 1055.05585, which is the same as multiplying by 0.00094781712.
How many joules are in 10 British thermal units?
10 BTU works out to 10550.558526 J.
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.