Megajoules to British Thermal Units
Type a value in either box to convert between megajoules and British thermal units. The factor is 947.817.
| Megajoules | British Thermal Units |
|---|---|
| 1 MJ | 947.81712 BTU |
| 2 MJ | 1895.634241 BTU |
| 3 MJ | 2843.451361 BTU |
| 5 MJ | 4739.085602 BTU |
| 10 MJ | 9478.171203 BTU |
| 25 MJ | 23695.428008 BTU |
| 50 MJ | 47390.856016 BTU |
| 100 MJ | 94781.712031 BTU |
How to use
- Enter a value in the Megajoules field.
- The British Thermal Units figure appears immediately — no button to press.
- Typing in the British Thermal Units field converts back to Megajoules the same way.
- Use the reference table for the values that come up most often.
Megajoules to British Thermal Units formula
The factor from megajoules to British thermal units is 947.81712.
BTU = MJ × 947.81712
Why this factor: the megajoule and the British thermal unit are both defined against the joule, so dividing one definition by the other gives 947.81712 directly. Both definitions are set out in full below.
To go the other way, divide by 947.81712 — or use the British Thermal Units to Megajoules converter, which is the same calculation reversed.
Worked example
Take 100 MJ and multiply by the factor 947.81712: the result is 94781.712031 BTU.
100 MJ × 947.81712 = 94781.712031 BTU
The converter above does this for any value you type, in either direction.
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.
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.
Megajoules vs British Thermal Units
The megajoule is a metric unit while the British thermal unit is a US customary 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 British thermal units are in a megajoule?
One megajoule equals 947.81712 British thermal units.
What is the formula to convert megajoules to British thermal units?
Multiply the number of megajoules by 947.81712. To reverse it, divide by 947.81712 instead.
How do I convert British thermal units back to megajoules?
Divide by 947.81712, which is the same as multiplying by 0.00105505585.
How many British thermal units are in 10 megajoules?
10 MJ works out to 9478.171203 BTU.
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 megajoule defined?
Exactly 1×10⁶ joules. One kilowatt-hour is exactly 3.6 MJ.