BTU to Kilojoules
Convert btu (BTU) to kilojoules (kJ). Both measure work and power, and the conversion comes up in nutrition, electricity, fitness work.
The Formula
``
kilojoules = btu × 1.05505585262
btu = kilojoules × 0.947817120313
`
One BTU is 1.0551 kilojoules, and one kilojoule is 0.947817 btu.
Conversion Table
| BTU | Kilojoules |
|---|---|
| 1 BTU | 1.0551 kJ |
| 2 BTU | 2.1101 kJ |
| 5 BTU | 5.2753 kJ |
| 10 BTU | 10.5506 kJ |
| 25 BTU | 26.3764 kJ |
| 50 BTU | 52.7528 kJ |
| 100 BTU | 105.5056 kJ |
| 500 BTU | 527.5279 kJ |
| 1,000 BTU | 1,055.06 kJ |
The Other Direction
| Kilojoules | BTU |
|---|---|
| 1 kJ | 0.947817 BTU |
| 2 kJ | 1.8956 BTU |
| 5 kJ | 4.7391 BTU |
| 10 kJ | 9.4782 BTU |
| 25 kJ | 23.6954 BTU |
| 50 kJ | 47.3909 BTU |
| 100 kJ | 94.7817 BTU |
| 500 kJ | 473.9086 BTU |
| 1,000 kJ | 947.8171 BTU |
What Each Unit Is
BTU (BTU) — the energy to raise one pound of water by one degree Fahrenheit, or 1,055 joules. The imperial thermal unit, still standard for US heating, cooling and gas.
Kilojoules (kJ) — 1,000 joules. The metric food-energy unit outside North America.
A Sense of Scale
A window air conditioner is 5,000–12,000 BTU/h- US furnaces are rated in BTU
- An apple holds about 400 kJ
- Daily intake is around 8,700 kJ
Doing It in Your Head
Multiply by 19, then divide by 18. That is off by 0.05% — close enough to judge a
distance, a weight or a price, and not close enough to sign off on a drawing.
Exact Mental shortcut 10.5506 kJ 10.5556 kJ 105.5056 kJ 105.5556 kJ
Precision
The factor 1.05505585262 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.
In Code
`javascript
const btuToKilojoule = (value) => value * 1.05505585262;
``
Where This Conversion Comes Up
- Nutrition
- Electricity
- Fitness
- Heating
- Fuel
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 BTU with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 BTU becomes | Error |
|---|---|---|---|
| 0 | 1 | 137 | 5.2183% |
| 1 | 1.1 | 150.7 | 4.2599% |
| 2 | 1.06 | 145.22 | 0.4686% |
| 3 | 1.055 | 144.535 | 0.0053% |
| 4 | 1.0551 | 144.549 | 0.0042% |
The right number of significant figures is set by your input, not by the converter. If you measured btu to three significant figures, the answer in kilojoules is only good to three — writing more digits claims precision the measurement never had.