British Thermal Units to Megajoules
Type a value in either box to convert between British thermal units and megajoules. The factor is 0.00105506.
| British Thermal Units | Megajoules |
|---|---|
| 1 BTU | 0.001055 MJ |
| 2 BTU | 0.00211 MJ |
| 3 BTU | 0.003165 MJ |
| 5 BTU | 0.005275 MJ |
| 10 BTU | 0.010551 MJ |
| 25 BTU | 0.026376 MJ |
| 50 BTU | 0.052753 MJ |
| 100 BTU | 0.105506 MJ |
How to use
- Enter a value in the British Thermal Units field.
- The Megajoules figure appears immediately — no button to press.
- Typing in the Megajoules 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 Megajoules formula
Converting British thermal units to megajoules is a single multiplication by 0.00105505585.
MJ = BTU × 0.00105505585
Why this factor: the British thermal unit and the megajoule are both defined against the joule, so dividing one definition by the other gives 0.00105505585 directly. Both definitions are set out in full below.
To go the other way, divide by 0.00105505585 — or use the Megajoules to British Thermal Units converter, which is the same calculation reversed.
Worked example
Start with 500 BTU. Multiply by 0.00105505585 to get 0.527528 MJ.
500 BTU × 0.00105505585 = 0.527528 MJ
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 megajoule?
A megajoule is one million joules, used for substantial energy quantities.
Definition: Exactly 1×10⁶ joules. One kilowatt-hour is exactly 3.6 MJ.
Where it is used: Fuel energy content, natural gas billing, and industrial energy accounting.
British Thermal Units vs Megajoules
The British thermal unit is a US customary unit while the megajoule 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 megajoules are in a British thermal unit?
One British thermal unit equals 0.00105505585 megajoules.
What is the formula to convert British thermal units to megajoules?
Multiply the number of British thermal units by 0.00105505585. To reverse it, divide by 0.00105505585 instead.
How do I convert megajoules back to British thermal units?
Divide by 0.00105505585, which is the same as multiplying by 947.81712.
How many megajoules are in 10 British thermal units?
10 BTU works out to 0.010551 MJ.
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.