Convert Joules to BTU
Joules to BTU is the conversion you reach for when energy in joules needs to match the British thermal units used for heating, cooling, and appliance ratings. One joule is approximately 0.000947817 BTU, so the BTU figure comes out much smaller.
Joules to British thermal units conversion table
| Joules (J) | British thermal units (BTU) |
|---|---|
| 1 | 0.000948 |
| 2 | 0.001896 |
| 3 | 0.002843 |
| 5 | 0.004739 |
| 10 | 0.009478 |
| 20 | 0.018956 |
| 50 | 0.047391 |
| 100 | 0.094782 |
| 500 | 0.473909 |
| 1,000 | 0.947817 |
The formula
To convert joules to BTU, multiply the number of joules by 0.0009478171203133172 (about 0.000947817):
BTU = joules × 0.0009478171203133172
A worked example
Say you have 10,000 joules and want it in BTU:
10000 × 0.0009478171203133172 = 9.4781712 BTU
So 10,000 joules is about 9.48 BTU.
Why it's an approximation
The factor 0.0009478171203133172 is a rounded value. Here's where it comes from: this tool uses the International Table BTU, defined as exactly 1055.05585262 joules. Converting joules to BTU means dividing by that number, which doesn't give a clean decimal, so the factor is rounded for practical use. On top of that, other BTU definitions differ by about 0.1%, so the everyday result is best treated as approximate.
When you'll use it
Matching energy in joules against the BTU ratings on furnaces, air conditioners, and other heating or cooling equipment, and comparing energy figures where one source uses joules and another uses BTU.
Frequently asked questions
How many joules are in a BTU?
This tool uses the International Table BTU, which is exactly 1055.05585262 joules. Other BTU definitions exist and differ by about 0.1%, so figures can vary slightly depending on the source.
Why are there different BTU definitions?
The BTU is based on heating a pound of water by one degree Fahrenheit, and that takes slightly different energy at different starting temperatures. This tool uses the International Table BTU (1055.05585262 joules); other versions differ by roughly 0.1%.
Is the joules to BTU conversion exact?
No. The factor 0.0009478171203133172 is rounded for everyday use, and it depends on which BTU definition you pick — this tool uses the International Table BTU, so treat the result as approximate.