Article — CCF to Therms Converter
CCF to Therms Conversion for Natural Gas
Converting CCF (100 cubic feet of natural gas) to therms requires the local heating value of the gas. The US national average is 1,038 BTU per cubic foot, so 1 CCF averages 1.038 therms. The exact ratio varies regionally — Puget Sound Energy customers see about 1.164 therms per CCF, while some SoCalGas customers see 1.025. The therm is an energy unit (100,000 BTU), CCF is a volume unit, and the heating value bridges them.
This calculator handles the conversion with adjustable BTU content so you can match your local utility instead of relying on the national average.
What are CCF and therms?
CCF stands for centum cubic feet — 100 ft³, the standard volume unit on most US gas bills. The therm is an energy unit equal to 100,000 BTU (British thermal units), which corresponds to 29.3 kWh or 105.5 megajoules. A therm is roughly the energy needed to heat 100 gallons of water from 60°F to 200°F.
Natural gas is sold by energy content (therms) in most retail markets because energy is what the customer actually consumes. But the meter physically measures volume, so utilities convert CCF to therms using a heating value (BTU per cubic foot) that accounts for the specific composition of the gas delivered.
The therm was originally defined in 1929 by the British Gas Industry as 100,000 BTU. It survives in US gas billing despite the BTU itself being non-SI. The closest SI equivalent is the megajoule: 1 therm = 105.506 MJ exactly using the international-table BTU.
CCF to therms math explained
The formula is straightforward. Multiply CCF by the heating value in BTU per cubic foot, then divide by 1000. The 1000 comes from 100 ft³/CCF × 1 therm/100,000 BTU = 1/1000 therm per (BTU/ft³).
For US average heating value: 1 CCF × 1,038 BTU/ft³ ÷ 1000 = 1.038 therms. If your utility uses a different heating value, plug that in instead. A 60 CCF winter month at 1,030 BTU/ft³ is 60 × 1.030 = 61.8 therms.
US average 1,038 BTU/ft³ → 1.038 therms/CCFLow end 1,010 BTU/ft³ → 1.010 therms/CCFPuget Sound 1,164 BTU/ft³ → 1.164 therms/CCFWhy the CCF-to-therm factor varies
Natural gas is mostly methane (CH₄), but real pipeline gas also contains ethane, propane, butane, nitrogen, and CO₂ in small amounts. The heavier hydrocarbons carry more energy per cubic foot, so gas with more ethane has a higher heating value. Gas from different production basins has different compositions.
Texas Gulf Coast gas tends to be drier (mostly methane, lower BTU). Pacific Northwest pipelines historically carried richer Canadian gas with higher BTU content. Liquefied natural gas (LNG) imports usually arrive at the high end of the heating-value range because lighter components evaporated during transport.
Reading CCF and therms on gas bills
Most utilities show both numbers. You will see meter readings in cubic feet, the difference in CCF or HCF, the local BTU factor (sometimes called thermal factor or pressure-volume correction factor), and the result in therms. The therm value is what gets multiplied by the per-therm rate to compute your gas charge.
Therms vs MMBTU vs kWh
Several energy units appear in gas-related discussions. The therm (100,000 BTU) is the retail unit. The MMBTU (1,000,000 BTU = 10 therms) is the wholesale unit — Henry Hub futures, pipeline tariffs, and industrial contracts all price in MMBTU. The kilowatt-hour (kWh) is the electric energy unit; converting helps compare gas heating to electric heating.
- 1 therm = 100,000 BTU = 29.3001 kWh = 105.506 MJ
- 1 MMBTU = 10 therms = 293.001 kWh
- 1 CCF (US avg) = 1.038 therms = 30.4 kWh equivalent
- 1 m³ natural gas ≈ 37.3 MJ ≈ 10.36 kWh (Wobbe number averaged)
- 1 kWh electricity = 3,412 BTU = 0.0341 therm
- 1 gallon propane ≈ 0.917 therms = 91,700 BTU
Regional heating values in the US
The Energy Information Administration tracks state-level heating values monthly. Most US states fall in the 1,025-1,045 BTU/ft³ range. Washington and Oregon historically run higher (1,100-1,200) because of Canadian pipeline gas. New England and the Mid-Atlantic tend to land at the national average because they receive a mix of Marcellus shale gas and Canadian imports.
If your bill doesn't explicitly print the BTU factor, you can back it out: divide the therms charged by the CCF used. A bill showing 80 CCF = 83.0 therms gives 1.038 — right at US average. If the ratio is far off (under 1.0 or over 1.2), double-check that you are comparing the same billing period.
CCF and therm cost math
To convert your bill back to per-CCF or per-therm rates: divide the total gas charge by your monthly therms (or CCF) to get the all-in price. US residential rates including delivery typically run $1.00-$3.00 per therm, which works out to $1.04-$3.11 per CCF. In Massachusetts and New York winter peaks the figure has hit $4-$5 per therm including delivery surcharges.
For wholesale comparisons, Henry Hub natural gas futures trade in dollars per MMBTU. A $3.00/MMBTU wholesale price corresponds to $0.30/therm or about $0.31/CCF before transportation, distribution, and retailer markup.
Common CCF/therm conversion mistakes
The most common error is treating CCF and therms as identical. They are within 4%, but at 100 CCF per month over a six-month heating season, that 4% adds up to several therms and tens of dollars. Always apply the heating-value factor.
CCF = 100 ft³; MCF = 1,000 ft³. If you mix them up, your therm math is off by a factor of 10. A 50 MCF month is really 50,000 ft³ = 500 CCF ≈ 519 therms — not 51.9 therms.
Another easy mistake is using kWh interchangeably with therms. The therm-to-kWh ratio is 29.3, so 50 therms is 1,465 kWh of gas energy, not 50 kWh. Confusing the two when comparing gas and electric heating gives dramatically wrong cost estimates.
One more pitfall is ignoring efficiency when comparing fuels by energy. Burning a therm of natural gas in a high-efficiency condensing furnace delivers about 95% of the energy as usable heat. The same therm in an old 70%-efficient furnace delivers only 70 kBTU of usable heat. A heat pump running on grid electricity at 1 kWh per 3-4 kWh of delivered heat outperforms both. When converting CCF or therms to "heating capacity," apply the appliance efficiency or you are comparing fuel energy, not delivered warmth.