Therms, Ccf, Mcf and MMBtu: Gas Units Explained

Utilities bill gas in Ccf (100 cubic feet) or therms (100,000 Btu), and wholesale markets quote it per MMBtu, a million Btu, which equals ten therms or one dekatherm. At the EIA’s 1,037 Btu per cubic foot, 1 Ccf is about 1.037 therms and 1 Mcf about 1.037 MMBtu, so the EIA’s $13.44 per Mcf winter residential price is roughly $1.30 per therm.

Two families of units exist because a meter can only count volume, while a fair price has to be set on heat. The bridge between them is the heat content of the gas actually delivered, which changes by place and by month, so no single factor is correct for every bill. A mountain utility adds a second bridge for altitude. Get either one wrong and a comparison between a bill, a tariff and the Henry Hub price can be off by several percent before any arithmetic starts. This page is only about the units and the factors between them. For the line items on a bill, see the natural gas bill guide; for how the cost-of-gas rate is set, see the purchased gas adjustment guide.

The units, in order of size

The EIA glossary defines MMBtu as one million British thermal units, Mcf as one thousand cubic feet and a therm as 100,000 Btu. Ccf is not in the glossary entries used here, but the EIA’s FAQ on the subject treats it as 100 cubic feet, the convention utilities use. The bridge between the volume rows and the heat rows is the heat content of the gas, Btu per cubic foot.

The EIA reports 1,036 Btu per cubic foot as the natural gas figure in its sample Btu conversion factors, and 1,037 as the U.S. annual average heat content of gas delivered to end users in 2025. The EIA’s own advice in the FAQ is that heat content varies by location, consumer type and time, and that the gas distributor may print the value on the bill. That is the right instruction. A national factor is good for comparing fuels and reading statistics; a bill needs the local one.

From meter dial to therms: one utility’s published method

Most descriptions of gas bills stop at “multiply by a factor.” Los Alamos County Public Utilities, a municipal utility in New Mexico, publishes the actual steps, and they show why the factor is two numbers rather than one. The utility serves customers at two different elevations, so the same meter reading represents different amounts of gas.

Step 1: correct the volume to sea-level conditions

Gas is compressed, and at high elevation the local air pressure is lower, so a cubic foot at the meter holds fewer molecules than a cubic foot at sea level. The utility multiplies the Ccf reading by an elevation factor: 0.81 for White Rock and 0.78 for the Los Alamos townsite. A 92.00 Ccf reading in White Rock becomes 74.520 sea-level Ccf, and in the townsite 71.760.

Step 2: convert sea-level volume to heat

The second factor converts sea-level Ccf to therms using the heat content of the gas. The utility’s worked example uses 1.054, which is a gas richer than the EIA’s national average of 1.037. The utility reports that the factor is reset each month from its supplier’s weighted averages, and it cites 1.0565 for October 2018 and 1.0520 for January 2018.

The difference between the two rows, 2.909 therms or about 3.7 percent, comes only from the elevation factor. Same reading, same gas, different pressure basis. Only the elevation factor appears on the customer’s bill, under “Multiplier,” according to the utility, and the current heat content factor is published on a monthly rate schedule. A reader who applies only the printed multiplier and ignores the monthly heat factor is off by the heat factor itself, five or six percent in this example.

Step 3: price the therms

Once the bill is in therms, the rate is dollars per therm. As an illustration only, if the commodity and delivery charges together equaled the EIA’s national winter average of $1.30 per therm, the White Rock customer’s 78.5 therms would cost about $101.80, and the townsite customer’s 75.6 therms about $98.03. Los Alamos charges its own rates, so this is arithmetic on a borrowed price, not the town’s bill. The reason for doing it is to see the order of magnitude: a household using 92 Ccf in a month pays on the order of a hundred dollars at the national average price.

Converting prices in every direction

Most confusion arises when a price quoted in one unit is compared with one in another. The conversion is always a division or multiplication by the heat content. At 1,037 Btu per cubic foot, the EIA’s $13.44 per Mcf becomes $1.34 per Ccf, $1.30 per therm and $12.96 per MMBtu. The same ladder works for wholesale quotes. The table starts from an MMBtu price, the unit in which futures and the Henry Hub spot price are quoted, and walks down to the bill units. The four starting prices are hypothetical round numbers, not market quotes.

A $4.00 wholesale gas price is $0.40 per therm. The household average of $1.30 per therm is more than three times that. The gap is not a markup on the commodity; it is the transport, distribution, storage, customer charges and taxes that a residential bill adds, a subject covered in the bill guide. The unit conversion only makes the comparison honest, so that the 3x gap is real and not an artifact of comparing a per-MMBtu price with a per-Mcf one.

The heat factor is not a constant: twelve states, one year

The 1,037 used above is a national average. The EIA publishes the heat content of gas delivered to consumers for each state, and the 2025 values run from 917 Btu per cubic foot in Hawaii, where much of the gas is synthetic, to 1,096 in Washington. The U.S. figure in that table is 1,036, one unit below the 1,037 in the EIA’s conversion FAQ, which counts a slightly different set of end-use sectors; both round to the same 1.04 therms per Ccf. The table below picks twelve states that span the range and applies each to a $4.00 per MMBtu price and to a 100 Ccf month.

Read across a row and the point is plain. A customer in Texas who burns 100 Ccf receives about 101.6 therms of heat; the same reading in Washington is 109.6 therms, 7.9 percent more heat for the same volume. A $4.00 per MMBtu contract is $4.064 per Mcf in Texas and $4.384 in Washington. Neither utility is overcharging: the gas is different. It is also why a per-Mcf price and a per-therm price from two states cannot be compared without the Btu content of each, and why a state commission that mixes Mcf and dekatherm rates in one table, as the Pennsylvania compilation did in its 2020-21 edition, needs a footnote on heat content.

Within one utility the factor moves far less than between states. Los Alamos County’s two published factors, 1.0565 for October 2018 and 1.0520 for January 2018, differ by about 0.4 percent, while the twelve states in Table 4 span more than 8 percent. A rough rule follows: use your own utility’s monthly factor when you have it, the state figure in Table 4 when you do not, and the national 1,036 or 1,037 only to compare fuels in general.

Commission orders quote dekatherms: translating them to the bill

Regulators and pipelines work in dekatherms, while the customer sees therms or Ccf. A dekatherm is exactly ten therms, so the first conversion needs no heat factor: divide by ten. Going to Ccf does need one, because a Ccf is a volume. The table converts five approved gas cost factors, the cost of the gas itself, from two Indiana orders (Cause Nos. 43629 GCA 77 and 37913 GCA 142, checked October 23, 2026). The heat content used for the Ccf column is the EIA’s 1,037 Btu per cubic foot, so the last column is an approximation that your utility’s own factor would adjust.

Two readings follow. First, the March 2026 NIPSCO factor of $4.283 per dekatherm is $0.4283 per therm, or about $0.444 per Ccf: a customer who burns 100 Ccf in a month, which is 103.7 therms, pays about $44.41 for the gas itself. Second, compare that with the EIA’s all-in $13.44 per Mcf, which is $1.296 per therm. The all-in figure is about three times the gas cost factor, and the difference is the delivery, customer, tax and rider charges that the bill guide itemizes. The Fountaintown line shows that a factor can sit anywhere in a wide range; the PGA guide explains why a factor of $1.6266 and one of $4.6561 appeared in the same quarter.

A winter of gas, in every unit

The EIA’s Winter Fuels Outlook gives the average natural-gas-heated household’s use and spending by month in Mcf and dollars. Converting the same months to the other units makes the ladder concrete and reveals how the all-in price per therm changes through the season. All rows use 1,037 Btu per cubic foot.

The household uses 48 Mcf over the season, which is 480 Ccf, about 498 therms or 49.8 MMBtu. Spending of $640 to $641 gives an all-in $1.29 per therm over the season. The monthly values are rounded to whole Mcf, so the per-therm column is approximate, but its shape is clear: the light months, November and March, come out at about $1.34 and $1.40 per therm, while the peak months of December and January come out near $1.23 and $1.28. The EIA’s own monthly price path points the same way, from $14.44 per Mcf in November down to $12.71 in January and back up to $13.81 in March. The table is a way to see the effect of units on a season, and a prompt to check whether a light month’s bill looks high per therm because of the price or because of rounding and fixed charges.

A units trap in a primary source

Unit labels can be wrong in official tables, and arithmetic is the defense. The EIA’s Winter Fuels Outlook 2026-27 gives the average natural gas household a winter consumption of 48 and a price of $13.44 per Mcf. In the table header, the consumption column is labeled “million cubic feet.” The prose around it uses Mcf, which the EIA defines as one thousand cubic feet. The way to decide is to multiply: 48 times $13.44 is $645, close to the $640 published, so the 48 is thousand cubic feet. If it were million cubic feet the bill would be $645,120, more than $645,000. The same kind of check works on any table: multiply quantity by price and see if the answer is believable.

Another real-world mismatch appears in state regulators’ own compilations. The Pennsylvania Public Utility Commission’s purchased gas cost compilation, in the 2020-21 edition cached on its site, lists several utilities’ approved rates in Mcf and another in dekatherms in the same table. Comparing those numbers directly would overstate or understate the price by 3.7 percent at 1,037 Btu per cubic foot, and by more where the supplier’s gas is richer. The check is to convert both to the same unit first, and to read the table notes for the heat content assumption.

One therm, in other fuels

The same Btu factors that bridge cubic feet to heat also bridge gas to other fuels. A single therm of natural gas holds the heat of the following amounts of other fuels, using the EIA’s published factors of 138,500 Btu per gallon of heating oil, 91,452 Btu per gallon of propane and 3,412 Btu per kilowatthour.

This is the shortcut behind comparisons like the heating fuel cost comparison: at 29.3 kWh to the therm, an electricity price of 18.23 cents per kWh means a therm of electric heat costs about $5.34 before efficiency, against $1.30 for gas at the same winter averages. Efficiency differences then narrow or widen the gap, which is the subject of that page.

A procedure for any quote you meet

1. Identify the base unit. Is the quote per cubic foot family (cf, Ccf, Mcf, MMcf) or per heat family (therm, Dth, MMBtu)?
2. Find the heat content. Look for Btu per cubic foot or a therms-per-Ccf factor on the bill or tariff. Without it, use 1,037 and say so.
3. Check for a pressure factor. High-altitude systems apply a multiplier before the heat content factor.
4. Convert once, to one unit. Choose therms or MMBtu and convert every figure in the comparison to it before doing any other arithmetic.
5. Multiply to sanity-check. Quantity times price should land near a believable bill. If it does not, suspect a label.

Data and sources: U.S. Energy Information Administration, FAQ on natural gas heat content and conversions, checked October 23, 2026 (about 1,037 Btu per cubic foot, 2025 U.S. delivered average; 1 Ccf about 1.037 therms; 1 Mcf about 1.037 MMBtu). EIA, British thermal units, checked October 23, 2026 (1,036 Btu per cubic foot; 138,500 Btu per gallon of heating oil; 91,452 Btu per gallon of propane; 3,412 Btu per kWh; therm 100,000 Btu). EIA, Glossary, checked October 23, 2026 (MMBtu, Mcf, therm). EIA, Winter Fuels Outlook 2026-27, released October 6, 2026, checked October 23, 2026 ($13.44 per Mcf, 48 per household, $640 average expenditure). Los Alamos County Public Utilities, Factors that Affect Natural Gas Measurement and Conversion to Therms, checked October 23, 2026 (elevation factors 0.81 and 0.78; heat content factor 1.054 in the example; 1.0565 for October 2018 and 1.0520 for January 2018). Pennsylvania Public Utility Commission, purchased gas cost compilation, 2020-21 cached edition, checked October 23, 2026 (rates listed in Mcf and in Dth). EIA, Heat Content of Natural Gas Delivered to Consumers, annual, release date September 30, 2026, checked October 23, 2026 (state values for 2025). All conversions, the worked bills and the price ladder are this page’s arithmetic. The wholesale prices in Table 3 are hypothetical.