Energy converter
British Thermal Units to Kilojoules
British Thermal Units and Kilojoules measure the same quantity in different unit systems. The relationship is 1 BTU = 1.055056 kJ, which gives 1.055056 kJ per BTU. Below you can convert any value, check a worked example and read the full chart.
Formula 1 BTU = 1.055056 kJ
Need the other direction? Kilojoules to British Thermal Units.
How to convert British Thermal Units to Kilojoules
The international table BTU is about 1,055.06 joules, used in heating and cooling. A kilojoule is 1,000 joules and appears on nutrition labels in many countries.
To convert British Thermal Units to Kilojoules, multiply the value in BTU by 1.055056. For example, 10 BTU × 1.055056 = 10.550559 kJ. This works because the ratio between the two units is constant for every value in energy.
Worked examples
| BTU | kJ |
|---|---|
| 1 BTU | 1.055056 kJ |
| 2.5 BTU | 2.63764 kJ |
| 5 BTU | 5.275279 kJ |
| 10 BTU | 10.550559 kJ |
| 25 BTU | 26.376396 kJ |
| 50 BTU | 52.752793 kJ |
| 100 BTU | 105.505585 kJ |
Reverse conversion
| kJ | BTU |
|---|---|
| 1 kJ | 0.94781712 BTU |
| 5 kJ | 4.739086 BTU |
| 10 kJ | 9.478171 BTU |
| 25 kJ | 23.695428 BTU |
| 50 kJ | 47.390856 BTU |
| 100 kJ | 94.781712 BTU |
When this conversion is useful
This is the calculation you need when you are comparing a nutrition label, an electricity bill or a heating system. Because the factor is fixed, you can use the same number for a single measurement or for a batch: 1,000 BTU is 1,055.06 kJ.
Is the conversion exact?
Yes for practical use: the factors come from international definitions, with rounding applied only for display.
Reference: BIPM SI Brochure and NIST SP 811. Last reviewed: 2026-11-01.
BTU to kJ conversion chart
The chart lists the most requested values. For a value that is not here, use the converter at the top of the page.
| British Thermal Units (BTU) | Kilojoules (kJ) |
|---|---|
| 1 BTU | 1.055056 kJ |
| 2 BTU | 2.110112 kJ |
| 3 BTU | 3.165168 kJ |
| 4 BTU | 4.220223 kJ |
| 5 BTU | 5.275279 kJ |
| 6 BTU | 6.330335 kJ |
| 7 BTU | 7.385391 kJ |
| 8 BTU | 8.440447 kJ |
| 9 BTU | 9.495503 kJ |
| 10 BTU | 10.550559 kJ |
| 11 BTU | 11.605614 kJ |
| 12 BTU | 12.66067 kJ |
| 13 BTU | 13.715726 kJ |
| 14 BTU | 14.770782 kJ |
| 15 BTU | 15.825838 kJ |
| 16 BTU | 16.880894 kJ |
| 17 BTU | 17.935949 kJ |
| 18 BTU | 18.991005 kJ |
| 19 BTU | 20.046061 kJ |
| 20 BTU | 21.101117 kJ |
| 21 BTU | 22.156173 kJ |
| 22 BTU | 23.211229 kJ |
| 23 BTU | 24.266285 kJ |
| 24 BTU | 25.32134 kJ |
| 25 BTU | 26.376396 kJ |
| 26 BTU | 27.431452 kJ |
| 27 BTU | 28.486508 kJ |
| 28 BTU | 29.541564 kJ |
| 29 BTU | 30.59662 kJ |
| 30 BTU | 31.651676 kJ |
| 31 BTU | 32.706731 kJ |
| 32 BTU | 33.761787 kJ |
| 33 BTU | 34.816843 kJ |
| 34 BTU | 35.871899 kJ |
| 35 BTU | 36.926955 kJ |
| 36 BTU | 37.982011 kJ |
| 37 BTU | 39.037067 kJ |
| 38 BTU | 40.092122 kJ |
| 39 BTU | 41.147178 kJ |
| 40 BTU | 42.202234 kJ |
| 41 BTU | 43.25729 kJ |
| 42 BTU | 44.312346 kJ |
| 43 BTU | 45.367402 kJ |
| 44 BTU | 46.422458 kJ |
| 45 BTU | 47.477513 kJ |
| 46 BTU | 48.532569 kJ |
| 47 BTU | 49.587625 kJ |
| 48 BTU | 50.642681 kJ |
| 49 BTU | 51.697737 kJ |
| 50 BTU | 52.752793 kJ |
| 60 BTU | 63.303351 kJ |
| 70 BTU | 73.85391 kJ |
| 80 BTU | 84.404468 kJ |
| 90 BTU | 94.955027 kJ |
| 100 BTU | 105.505585 kJ |
Frequently asked questions
How many Kilojoules are in 1 British Thermal Units?
1 BTU equals 1.055056 kJ.
How do I convert British Thermal Units to Kilojoules?
Multiply the BTU value by 1.055056. Example: 25 BTU = 26.376396 kJ.
What is 2.5 BTU in kJ?
2.5 BTU = 2.63764 kJ.
Is the BTU to kJ conversion exact?
Yes for practical use: the factors come from international definitions, with rounding applied only for display.
Does the calculator work offline?
Yes. The conversion runs in your browser with JavaScript, so it works after the page has loaded, even without a connection.