Cost Per Therm Calculator
Two households on the same street can pay the same gas rate on paper and still end up with very different bills, because fixed charges, delivery fees, and taxes hide inside the total. Dividing the whole bill by the therms you used strips that away: you get one honest number, your true cost per therm, that you can track month to month and compare against any supplier offer.
Enter the total from your most recent natural gas bill and the therms shown on it. The calculator returns your all-in cost per therm and places it against recent US averages, so you can tell whether you are paying a normal price or an outlier.
How it was calculated
This is the all-in figure: it counts every dollar on the bill, not just the supply rate your utility advertises. That is the number that matters for budgeting and for spotting billing surprises.
Quick Answer
Key takeaways
- Cost per therm is the whole bill divided by therms used. It is the only version of your gas price that counts delivery, service charges, and taxes.
- Regulators use the same all-in method: the Georgia Public Service Commission defines the true cents-per-therm as the total bill before taxes divided by therms used.
- Averages give the number meaning: about $1.40 per therm for US residential customers and $0.97 for commercial customers in 2024, converted from EIA prices per Mcf.
- Your per-therm cost moves even when your rate does not, because the fixed monthly customer charge is spread over more therms in winter and fewer in summer.
- Quick Answer
- How to use the cost per therm calculator
- The formula, and the two honest ways to count a bill
- Worked example: a $135 bill and 60 therms
- If your bill shows Ccf or Mcf instead of therms
- How your number compares with US averages
- What competing calculators miss
- Two levers: pay less per therm, or use fewer therms
- Frequently Asked Questions
- Add This Calculator to Your Website
- References
How to use the cost per therm calculator
Start with the bill itself, not your utility's advertised rate. The advertised rate is usually only the supply charge, and it leaves out the delivery and fixed fees that make up a large share of what you actually pay.
Find the total. Take the full amount due for the billing period: supply, delivery, customer charge, riders, and taxes together.
Find the therms. Look in the usage or meter section of the same bill for therms used. If the bill shows Ccf instead, use the conversion table further down this page before entering anything.
Enter both numbers and calculate. The result is your all-in cost per therm for that period, with a verdict that places it against recent US averages.
Repeat each month. A single month can mislead. Three or four months in a row show whether a high figure was weather, a rate change, or a billing error.
Property managers and businesses can run the same steps per meter or per building. The math does not change; only the size of the numbers does.
The formula, and the two honest ways to count a bill
The formula is a single division, and the only real decision is what goes into the total.
All-in (the method this calculator uses). Divide the entire bill by therms. This is the approach the Georgia Public Service Commission recommends for its true cents-per-therm comparison, because it puts every supplier on a level field: a low supply rate cannot hide behind high delivery or service fees. Use the all-in figure for budgeting and for spotting unusual bills.
Supply-only. Divide only the gas supply or commodity charge by therms. This figure always reads lower, and it is the right one for comparing supplier offers in a deregulated market, where delivery stays with the same utility no matter who sells you the gas. What you must not do is mix the two: comparing one supplier's all-in figure with another's supply-only rate will always crown the supply-only number, fairly or not.
Worked example: a $135 bill and 60 therms
The calculator is pre-filled with this case, and every figure below is what it returns.
| Item | Value | Reading |
|---|---|---|
| Total cost (whole bill) | $135.00 | Supply, delivery, charges, and taxes |
| Therms used | 60 | From the usage section of the bill |
| Cost per therm ($135.00 / 60) | $2.25 | High |
| 2024 US residential average | $1.40 | EIA price converted from $ per Mcf |
| Gap vs residential average | +$0.85 (61% higher) | Worth investigating, not proof of an error |
Two other bills show how much the figure moves with the season, using the same calculator:
| Bill | Total cost | Therms | Cost per therm |
|---|---|---|---|
| Mild-month bill | $96.00 | 80 | $1.20 Typical |
| Worked example | $135.00 | 60 | $2.25 High |
| Cold-month bill | $180.00 | 120 | $1.50 Above average |
The cold-month bill is the biggest of the three and still not the most expensive per therm. That pattern is normal: the fixed customer charge is the same every month, so in a high-usage month it is divided across more therms and each therm carries less of it. A $15 fixed charge adds $0.50 per therm to a 30-therm month but only $0.10 per therm to a 150-therm month. If your per-therm figure spikes in a mild month while your rate stayed flat, this dilution effect is the first explanation to check, before assuming a billing error. For the heat content behind each therm, the cost per BTU calculator breaks the same energy down to the single-BTU level used in appliance and HVAC comparisons.
If your bill shows Ccf or Mcf instead of therms
Some utilities bill by volume, not energy. The conversions rest on the average heat content of US natural gas: according to the U.S. Energy Information Administration's conversion guidance, gas delivered to end users averaged about 1,037 Btu per cubic foot in 2025, so 100 cubic feet (1 Ccf) holds about 1.037 therms and 1,000 cubic feet (1 Mcf) holds about 10.37 therms. Your own utility prints its exact therm factor on the bill, and that factor beats the national average when the two differ.
| Your bill shows | Convert to therms | Convert a price to $ per therm |
|---|---|---|
| Ccf (100 cubic feet) | Ccf x 1.037 | $ per Ccf / 1.037 |
| Mcf (1,000 cubic feet) | Mcf x 10.37 | $ per Mcf / 10.37 |
| MMBtu (1,000,000 Btu) | MMBtu x 10 | $ per MMBtu / 10 |
| Therms | No conversion needed | Enter the bill directly |
So a supplier quoting $14.50 per Mcf is quoting $14.50 / 10.37 = $1.40 per therm, directly comparable with the figure this calculator gives you. The same unit discipline applies to electricity: 1 therm holds the heat equivalent of about 29.3 kWh, and running your electric bill through the cost per kWh calculator lets you compare gas heat with electric heat on one energy basis instead of guessing from two unrelated bills.
How your number compares with US averages
A cost per therm means little until it sits next to a benchmark. The EIA publishes delivered natural gas prices per thousand cubic feet; dividing by 10.37 therms per Mcf puts them on the same basis as your bill.
State averages sit far apart. EIA state price series for 2025 put residential gas in North Dakota at $9.50 per Mcf (about $0.92 per therm) and California at $22.01 per Mcf (about $2.12 per therm), so a figure that looks high nationally can be ordinary in a high-cost state, and the reverse. Judge your bill first against your own past bills, then against your state's average, and only then against the national one. To see where gas sits inside your whole household energy spend, the cost of energy calculator totals the fuels together.
What competing calculators miss
The top-ranking tools for this keyword all do the same division. The differences are in what surrounds it, and several have real problems.
A worked example that produces $60 per therm. One top result builds its formula on cubic feet instead of the therms printed on your bill, and its own example lands on a $60 per therm figure, roughly forty times what US households pay, without flagging it. A reader who trusts that example walks away with a broken sense of the scale.
Implausible results presented as normal. Another ranking calculator works an example at $11.74 per therm and moves on. Small therm counts do inflate the all-in figure, as the fixed-charge section above explains, but a responsible page says so instead of presenting an outlier as a routine outcome.
No distinction between all-in and supply-only. The bare tools never tell you which total to enter, so two readers with identical bills can get different answers depending on which line they typed. This page fixes one method, names it, and explains when the other method is the right choice.
No benchmark. A result of $2.25 is only useful if you know the residential average is about $1.40. The verdict in the calculator and the benchmark table above supply that context, and the Ccf and Mcf conversions cover the many bills that never print the word therm at all.
Two levers: pay less per therm, or use fewer therms
A high result points at one of two problems, and the fixes are different. If your supply rate is the issue and your state lets you choose a gas supplier, compare offers on the all-in basis described above, not on the headline supply rate. Delivery charges do not change when you switch suppliers, so the honest comparison is supply charge per therm, added to the delivery figure you already pay.
If the rate is normal but the bill is heavy, the lever is usage: a programmable thermostat, sealed duct leaks, and insulation in the attic cut therms directly. One caution on reading the results afterward: using fewer therms lowers your total bill but can raise your all-in cost per therm slightly, because the fixed customer charge gets spread over fewer units. The bill is what you pay; the per-therm figure is the diagnostic. Judge an efficiency upgrade by the bill, and use this calculator to keep the rate itself honest.
Frequently Asked Questions
A therm is a unit of heat energy equal to 100,000 British thermal units (Btu). US gas utilities bill in therms because the measure counts the heat the gas delivers, not just the volume that passed through the meter, and volumes with different heat content are then billed fairly.
Look in the usage or meter-reading section of the bill, where most utilities print therms used for the period next to the meter readings. If your bill shows Ccf instead, multiply the Ccf figure by your utility's therm factor, about 1.037 on national average heat content, and enter the result.
For a household, around the US residential average is a good result: about $1.40 per therm in 2024 on EIA figures. Under $1.00 per therm is low, $1.00 to $1.80 is the typical residential band, and above $1.80 is high, though state averages run from about $0.92 in North Dakota to about $2.12 in California, so compare with your state first.
Enter the whole bill if you want your true all-in cost, which is the figure to use for budgeting and month-to-month tracking. Enter only the supply charge if you are comparing gas suppliers in a deregulated market. Pick one method and use it consistently, because the two figures are not comparable with each other.
Convert first: multiply your Ccf by 1.037, the EIA average heat content factor, or by the exact therm factor printed on your bill. A bill for 58 Ccf converts to about 60.1 therms, which you can enter directly. For Mcf, multiply by 10.37 instead.
Because of the fixed monthly customer charge. It is the same dollar amount every month, so it adds far more per therm in a low-usage month than in a high-usage one: a $15 charge adds $0.50 per therm at 30 therms but only $0.10 per therm at 150 therms. Seasonal swings in the all-in figure are normal even on a fixed rate.
One MMBtu is 1,000,000 Btu, which is exactly 10 therms. Multiply a per-therm price by 10 to get the per-MMBtu price: the $2.25 per therm in the worked example equals $22.50 per MMBtu. Wholesale gas prices are quoted per MMBtu, but those are commodity prices that exclude delivery, so they always read far below a household bill figure.
Yes. Any gas bill stated in therms works, from a restaurant or laundry to a small factory. Commercial customers paid about $0.97 per therm on average in 2024 (EIA), lower than residential customers, because larger and steadier volumes carry lower delivery costs per unit.
Add This Calculator to Your Website
References
- U.S. Energy Information Administration, "How do I convert natural gas prices in dollars per cubic feet to dollars per British thermal unit or therm?" - heat content of 1,037 Btu per cubic foot, 1 Ccf = 1.037 therms, 1 Mcf = 10.37 therms, and the price conversion formulas used on this page. EIA: Natural gas price conversion FAQ. Accessed October 2026.
- U.S. Energy Information Administration, "Natural Gas Monthly, Table 3: Selected National Average Natural Gas Prices" - 2024 annual average delivered prices of $14.50 per Mcf residential and $10.07 per Mcf commercial, converted on this page to $1.40 and $0.97 per therm. EIA: Natural Gas Monthly Table 3 (PDF). Accessed October 2026.
- Georgia Public Service Commission, "The True Cents-Per-Therm" - the regulator's definition of the all-in cost per therm as the total bill before taxes divided by therms used, the method this calculator follows. Georgia PSC: The True Cents-Per-Therm. Accessed October 2026.
- U.S. Energy Information Administration, "California Price of Natural Gas Delivered to Residential Consumers" - state price series showing $22.01 per Mcf for 2025, about $2.12 per therm. EIA: California residential natural gas prices. Accessed October 2026.
- U.S. Energy Information Administration, "North Dakota Price of Natural Gas Delivered to Residential Consumers" - state price series showing $9.50 per Mcf for 2025, about $0.92 per therm. EIA: North Dakota residential natural gas prices. Accessed October 2026.