How to Convert Joules to British thermal units (J to BTU)
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 joules into british thermal units by hand, with examples and a quick-reference table.
The conversion
To convert joules to british thermal units, multiply the value by 0.0009478171. To go the other way, divide by the same number (or multiply by 1,055.05585). Because the factor is tiny, scientific notation keeps the numbers manageable.
British thermal units = joules × 0.0009478171
Worked examples
- 3 J = 0.002843 BTU
- 12.5 J = 0.011848 BTU
- 75 J = 0.071086 BTU
Joules to British thermal units table
| Joules | British thermal units |
|---|---|
| 1 J | 0.000948 BTU |
| 2 J | 0.001896 BTU |
| 5 J | 0.004739 BTU |
| 10 J | 0.009478 BTU |
| 20 J | 0.018956 BTU |
| 25 J | 0.023695 BTU |
| 50 J | 0.047391 BTU |
| 100 J | 0.094782 BTU |
| 250 J | 0.236954 BTU |
| 500 J | 0.473909 BTU |
| 1,000 J | 0.947817 BTU |
Common questions
Is J to BTU 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 British thermal units to Joules converter.
Mistakes to avoid
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.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
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.
Background
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.
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.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For any value, use the Joules to British thermal units Converter or browse all energy converters.
Run your own numbers: Joules to British thermal units Converter