Convert Calories to Therms
1 calorie (cal) equals 3.966613703 × 10⁻⁸ therms (thm).
1 cal = 3.966613703e-8 thm
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk calorie to therm converter to paste a column from Excel.
How to Convert Calorie to Therm
- 1 cal = 3.966613703 × 10⁻⁸ thm
- 1 thm = 25210420.65 cal
- Example: convert 15 cal to thm: 15 cal = 15 × 3.966613703 × 10⁻⁸ thm = 5.949920554 × 10⁻⁷ thm
Reference conditions. cal: Thermochemical calorie, 4.184 J exactly. The International Table calorie is 4.1868 J. thm: US therm, 100 000 BTU (59 °F), 105.4804 MJ as given by NIST SP 811. The EC therm is 105.506 MJ.
Formula
thm = cal × 3.96661370264 × 10⁻⁸
or thm = cal ÷ 25210420.6501
Derivation from SI units:
- 1 cal (thermochemical) = 4.184 J (exact)
- 1 thm (US) = 1.054804 × 10⁸ J (NIST SP 811)
- 1 cal = 4.184 J ÷ 105480400 J per thm = 3.96661370264 × 10⁻⁸ thm
Both units are defined exactly, so the factor is exact. Calorie definition: calorie; Therm definition: therm.
Worked examples
- A reading of 100 cal converts to 0.000003966613703 thm.
100 cal × 3.966613703 × 10⁻⁸ = 0.000003966613703 thm - A value of 1000 cal is 0.00003966613703 thm.
1000 cal × 3.966613703 × 10⁻⁸ = 0.00003966613703 thm
Calorie to Therm conversion table
| Calories (cal) | Therms (thm) |
|---|---|
| 1 cal | 3.966613703 × 10⁻⁸ thm |
| 10 cal | 3.966613703 × 10⁻⁷ thm |
| 100 cal | 0.000003966613703 thm |
| 250 cal | 0.000009916534257 thm |
| 500 cal | 0.00001983306851 thm |
| 1000 cal | 0.00003966613703 thm |
| 4184 cal | 0.0001659631173 thm |
| 10000 cal | 0.0003966613703 thm |
Where it's used
Calories are used for chemistry and calorimetry, while therms appear in US and UK natural-gas bills. Both measure energy, work and heat, so the conversion is a fixed factor.
Calorie to other energy units
| Conversion | 1 cal equals |
|---|---|
| calorie to joule | 4.184 J |
| calorie to kilojoule | 0.004184 kJ |
| calorie to megajoule | 0.000004184 MJ |
| calorie to kilocalorie | 0.001 kcal |
| calorie to watt-hour | 0.001162222222 Wh |
| calorie to kilowatt-hour | 0.000001162222222 kWh |
| calorie to BTU | 0.003965666831 BTU |
| calorie to therm | 3.966613703 × 10⁻⁸ thm |
| calorie to electronvolt | 2.611447397 × 10¹⁹ eV |
| calorie to foot-pound | 3.085960033 ft·lbf |
| calorie to erg | 41840000 erg |
Frequently asked questions
How many therms are in 1 calorie?
1 cal = 3.966613703 × 10⁻⁸ thm.
How do I convert calories to therms?
Multiply the value in cal by 3.966613703 × 10⁻⁸, or divide it by 25210420.65. For example, 15 cal × 3.966613703 × 10⁻⁸ = 5.949920554 × 10⁻⁷ thm.
Is the cal to thm 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, "calorie (thermochemical) (cal_th)".
- 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.)".
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 Calories to Therms. Retrieved October 17, 2026, from https://scientificconverters.com/energy/calories-to-therms/
IEEE
Scientific Converters, "Convert Calories to Therms," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/energy/calories-to-therms/