A therm is 100,000 Btu. An Mcf is 1,000 cubic feet. If the utility or EIA gives a price in dollars per Mcf and a heat content in Btu per cubic foot, dollars per therm ≈ ($/Mcf) ÷ (heat content ÷ 100). Equivalently, therms per Mcf = heat content ÷ 100, then divide the Mcf price by that. EIA’s FAQ on this conversion (FAQ 45) discusses the method and rounds the U.S. 2025 average heat content to about 1,037 Btu/cf; the annual series this site uses reports a U.S. 2025 average of 1,036 Btu/cf, or about 10.36 therms in an Mcf. At the 2025 U.S. average residential gas price of $15.34/Mcf, that is about 1.48 per therm.
| Place | $/Mcf | Btu/cf | Therms per Mcf | Implied $/therm |
|---|---|---|---|---|
| United States | 15.34 | 1036 | 10.36 | 1.48 |
| Illinois | 11.25 | 1048 | 10.48 | 1.07 |
| Texas | 19.42 | 1016 | 10.16 | 1.91 |
If your bill is already in $/therm, skip the conversion and enter that number. If it is in $/Ccf (hundred cubic feet), ten Ccf are one Mcf, so multiply $/Ccf by ten to get $/Mcf, then convert, or divide $/Ccf by (heat content ÷ 1,000). Then put the therm price into the calculator with the furnace AFUE. Some utilities print the heat content on the bill; prefer that figure when it is there.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.