How to Convert British thermal units to Joules (BTU to J)
Energy conversions link food labels in kJ and kcal, SP Group bills in kWh and air-conditioner capacity in BTU. This guide shows how to convert british thermal units into joules by hand, with examples and a quick-reference table.
The conversion
To convert british thermal units to joules, multiply the value by 1,055.05585. To go the other way, divide by the same number (or multiply by 0.0009478171). For a quick estimate, multiply by about 1,100.
Joules = british thermal units × 1,055.05585
Worked examples
- 3 BTU = 3,165.17 J
- 12.5 BTU = 13,188.2 J
- 75 BTU = 79,129.19 J
British thermal units to Joules table
| British thermal units | Joules |
|---|---|
| 1 BTU | 1,055.06 J |
| 2 BTU | 2,110.11 J |
| 5 BTU | 5,275.28 J |
| 10 BTU | 10,550.56 J |
| 20 BTU | 21,101.12 J |
| 25 BTU | 26,376.4 J |
| 50 BTU | 52,752.79 J |
| 100 BTU | 105,505.58 J |
| 250 BTU | 263,763.96 J |
| 500 BTU | 527,527.92 J |
| 1,000 BTU | 1,055,055.85 J |
Common questions
Is BTU to J exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Joules to British thermal units converter.
Mistakes to avoid
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Dropping the units
A bare number without a unit is easy to misread later. Always write the unit with the result.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Background
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
For any value, use the British thermal units to Joules Converter or browse all energy converters.
Run your own numbers: British thermal units to Joules Converter