Natural Gas Bill Calculator: Therms, Ccf and Mcf

The three units on gas bills

• Therm — 100,000 Btu of heat. Most utilities bill in therms because it measures the energy you actually received.
• Ccf — 100 cubic feet, what many meters count. A ccf holds about one therm — exactly Btu per cubic foot ÷ 1,000 therms, or 1.036 at the 2025 U.S. heat content.
• Mcf — 1,000 cubic feet, the unit EIA publishes prices in. One Mcf = 10 ccf.

The conversions follow EIA’s own method [8]: $ per Mcf ÷ (Btu per cubic foot ÷ 100) = $ per therm, and $ per Mcf ÷ 10 = $ per ccf. The heat content differs by state — from 917 to 1,096 Btu per cubic foot [7] — so the calculator converts with your state’s value rather than a national constant.

Worked example

A meter reading of 60 ccf for the month, priced at the U.S. average of $1.534 per ccf ($15.34 per Mcf ÷ 10): 60 × $1.534 = $92.04. In therms that is 60 × 1.036 = 62.2 therms at $1.481.

Why a summer therm costs more than a winter one

EIA’s residential price is revenue ÷ volume, and your gas bill carries a fixed monthly charge whether you burn gas or not. In summer the volume is tiny, so the average price per unit jumps: the U.S. residential price was $26.45 per Mcf in July 2026 against the 2025 annual average of $15.34 [4]. The bill itself is still smallest in summer.

Residential deliveries show the pattern [5]: in 2025, December through February carried 54.85% of the year’s residential gas, June through August only 7.13%. Use the annual price with annual (or 12-month average) usage, as the calculator does, and the two effects cancel.