Convert Therms to BTU
1 therm (thm) equals 99976.12898 British thermal units (BTU).
1 thm = 99976.12898 BTU
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk therm to BTU converter to paste a column from Excel.
How to Convert Therm to BTU
- 1 thm = 99976.12898 BTU
- 1 BTU = 0.00001000238767 thm
- Example: convert 15 thm to BTU: 15 thm = 15 × 99976.12898 BTU = 1499641.935 BTU
Reference conditions. thm: US therm, 100 000 BTU (59 °F), 105.4804 MJ as given by NIST SP 811. The EC therm is 105.506 MJ. BTU: International Table BTU (BTU_IT), 1055.05585262 J exactly.
Formula
BTU = thm × 99976.1289775
Derivation from SI units:
- 1 thm (US) = 1.054804 × 10⁸ J (NIST SP 811)
- 1 BTU_IT = 1055.05585262 J (exact)
- 1 thm = 105480400 J ÷ 1055.05585262 J per BTU = 99976.1289775 BTU
Both units are defined exactly, so the factor is exact. Therm definition: therm; BTU definition: British thermal unit.
Worked examples
- A reading of 20 thm converts to 1999522.58 BTU.
20 thm × 99976.12898 = 1999522.58 BTU - A value of 100 thm is 9997612.898 BTU.
100 thm × 99976.12898 = 9997612.898 BTU
Therm to BTU conversion table
| Therms (thm) | BTU |
|---|---|
| 1 thm | 99976.12898 BTU |
| 5 thm | 499880.6449 BTU |
| 10 thm | 999761.2898 BTU |
| 20 thm | 1999522.58 BTU |
| 50 thm | 4998806.449 BTU |
| 75 thm | 7498209.673 BTU |
| 100 thm | 9997612.898 BTU |
| 500 thm | 49988064.49 BTU |
| 1000 thm | 99976128.98 BTU |
Where it's used
Therms are used for US and UK natural-gas bills, while British thermal units appear in furnace, boiler and fuel ratings in the US. Both measure energy, work and heat, so the conversion is a fixed factor.
Therm to other energy units
| Conversion | 1 thm equals |
|---|---|
| therm to joule | 105480400 J |
| therm to kilojoule | 105480.4 kJ |
| therm to megajoule | 105.4804 MJ |
| therm to calorie | 25210420.65 cal |
| therm to kilocalorie | 25210.42065 kcal |
| therm to watt-hour | 29300.11111 Wh |
| therm to kilowatt-hour | 29.30011111 kWh |
| therm to BTU | 99976.12898 BTU |
| therm to electronvolt | 6.583568738 × 10²⁶ eV |
| therm to foot-pound | 77798350.53 ft·lbf |
| therm to erg | 1.054804 × 10¹⁵ erg |
Frequently asked questions
How many British thermal units are in 1 therm?
1 thm = 99976.12898 BTU.
How do I convert therms to British thermal units?
Multiply the value in thm by 99976.12898. For example, 15 thm × 99976.12898 = 1499641.935 BTU.
Is the thm to BTU conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "therm (U.S.)".
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "British thermal unit_IT (Btu_IT)".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Therms to BTU. Retrieved October 17, 2026, from https://scientificconverters.com/energy/therms-to-btu/
IEEE
Scientific Converters, "Convert Therms to BTU," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/therms-to-btu/