People type this into search every day: gas bill calculator.
The usual answer is “therms times the rate.” That is the usage line. The statement also has a daily standing charge, and often a tax.
This page is a labeled estimate. It is not your utility tariff, and it is not a weather forecast.
Usage, standing charge, then tax
The gas bill estimate calculator uses:
(usage × rate + daily charge × days) × (1 + tax)
Usage is already converted to the billed energy unit. The tool bills that unit as kWh. Tiered rates and credits are excluded. Those are the tool’s assumptions.
Some US statements still print therms or Ccf. EIA’s energy conversion calculators put a therm at 100,000 Btu. A kilowatt-hour is 3,412 Btu. 100,000 ÷ 3,412 = 29.3 kWh per therm. Convert first, then type the kWh.
Fig 1
Three lines, one bill
Usage first, standing charge second, tax last
850 kWh at $0.09 plus $0.45 for 30 days is $90.00 before 5% tax, then $94.50.
EIA’s October 2026 Winter Fuels Outlook is the winter context I am using, not a substitute for your rate. They forecast $640 as the US average November-through-March spend for households that heat mainly with natural gas, 9% below the previous winter. They also cite the Census ACS figure that natural gas was the main heat in 46% of US homes in 2024. $640 over those five months is $128 a month as a national winter average. The calculator default is a milder $94.50 month. A heating month in the examples below is $184.28.
Their natural gas monthly Table 20 is the state-by-state residential price series. Those prices are per thousand cubic feet and already mix commodity, delivery, and tax. Type the unit rate and the standing charge from your own statement.
Example 1: the published $94.50 month
Here are the calculator defaults:
- monthly gas use: 850 kWh
- usage rate: $0.09 / kWh
- daily standing charge: $0.45
- billing days: 30
- tax and surcharge: 5%
Usage charge: 850 × 0.09 = $76.50
Standing charge: 0.45 × 30 = $13.50
Subtotal: $90.00
Tax: 90 × 0.05 = $4.50
Bill: $94.50
850 kWh is 850 ÷ 29.3 = 29.0 therms. At $0.09 / kWh the therm is 0.09 × 29.3 = $2.64.
Calculator result
Gas bill estimate
- Monthly gas use
- 850 kWh
- Usage rate
- $0.09
- Daily standing charge
- $0.45
- Billing days
- 30 days
- Tax and surcharge
- 5%
$94.50
estimated gas bill
- Usage charge
- $76.50
- Standing charge
- $13.50
A year of that month, with no seasonal change, is 94.50 × 12 = $1,134.00. Real houses do not do that. Winter and summer sit in the next two examples.
Fig 2 · 1/3
The $94.50 default bill
850 kWh at $0.09, $0.45 a day, 30 days, 5% tax
Usage
$76.50
Standing
$13.50
Tax
$4.50
Usage is $76.50.
Standing charge is $13.50. Tax is $4.50.
Example 2: a winter heating month
Keep $0.09, $0.45, 30 days, 5%. Set usage to 1,800 kWh.
Usage charge: $162.00
Standing charge: $13.50
Subtotal: $175.50
Bill: $184.28
Calculator result
Gas bill estimate
- Monthly gas use
- 1800 kWh
$184.28
estimated gas bill
- Usage charge
- $162.00
- Standing charge
- $13.50
1,800 kWh is 1,800 ÷ 29.3 = 61.4 therms. Five months like this would be 184.28 × 5 = $921.40, above EIA’s $640 US average. That average mixes mild and cold states. This 1,800 kWh month is a cold-house planning number, not EIA’s forecast.
Example 3: a summer month
200 kWh, same rate and standing charge.
Usage charge: $18.00
Standing charge: $13.50
Subtotal: $31.50
Bill: $33.08
Standing charge is now 13.50 / 31.50 = 42.9% of the subtotal. In winter it was 13.50 / 175.50 = 7.7%.
Fig 3 · 1/4
Three seasons, one tariff
$0.09 / kWh, $0.45 a day, 30 days, 5% tax
- Monthly bill
| Category | Monthly bill |
|---|---|
| Summer 200 | $33 |
| Default 850 | $95 |
| Mild 1,200 | $128 |
| Winter 1,800 | $184 |
Summer 200 kWh is $33.08.
Winter 1,800 kWh is $184.28.
Example 4: a 31-day month
Keep 850 kWh and $0.09. Set days to 31.
Standing charge: 0.45 × 31 = $13.95
Subtotal: 76.50 + 13.95 = $90.45
Bill: $94.97
The extra day is $0.45 × 1.05 = $0.47. Usage did not change.
A 28-day February at the same 850 kWh is $93.55. Standing charge falls to $12.60.
Example 5: what if the unit rate moves to $0.12
Hold 850 kWh, $0.45, 30 days, 5%. Change only the rate.
Usage charge: $102.00
Bill: $121.28
The jump is 121.28 − 94.50 = $26.78, which is 850 × 0.03 × 1.05. Standing charge did not move.
Example 6: no standing charge
Some statements fold delivery into the unit rate and print $0.00 on the daily line.
Usage charge: $76.50
Standing charge: $0.00
Bill: $80.33
That is $14.17 below the default. The $14.17 is 13.50 × 1.05.
Fig 4 · 1/2
The standing charge on an 850 kWh month
Same $0.09 rate and 5% tax
Estimated bill
No standing charge
$80.33
Default $0.45 / day
$94.50
Usage only is $80.33.
Adding $0.45 a day brings the bill to $94.50.
Example 7: drop the 5% tax
Keep the default 850 kWh month. Set tax to 0.
Bill: $90.00
Tax on the default was $4.50. Some US gas prices in EIA Table 20 already include tax. If you copy a tax-inclusive unit rate and then add 5% again, you double-count.
Example 8: the common mistake, ignore the standing charge at low use
A vacant month, or a house that shut the valve, still has a daily line.
Usage: 0 kWh
Standing charge: $13.50
Bill: $14.18
Calculator result
Gas bill estimate
- Monthly gas use
- 0 kWh
$14.18
estimated gas bill
- Usage charge
- $0.00
- Standing charge
- $13.50
If you budget “no gas, no bill,” you miss $14.18. Over a year of empty months that is 14.18 × 12 = $170.16.
Fig 5 · 1/2
Standing charge does not clock out
Same $0.45 a day and 5% tax
- Usage after tax
- Standing after tax
| Category | Usage after tax | Standing after tax |
|---|---|---|
| 0 kWh | $0.00 | $14 |
| 200 kWh | $19 | $14 |
| 850 kWh | $80 | $14 |
| 1,800 kWh | $170 | $14 |
Zero use is still $14.18.
Winter 1,800 kWh is $184.28, and $13.50 of standing charge is still in it.
Usage after tax is usage × 0.09 × 1.05. Standing after tax is 13.50 × 1.05 = 14.175 on every bar.
Example 9: a 61-day two-month bill
Some statements cover two calendar months.
- usage: 1,700 kWh
- days: 61
Usage charge: $153.00
Standing charge: 0.45 × 61 = $27.45
Subtotal: $180.45
Bill: $189.47
Two default 30-day months would have been 94.50 × 2 = $189.00 on 1,700 kWh and 60 days. The extra day adds $0.45 × 1.05 = $0.47. 189.00 + 0.47 = 189.47.
Example 10: a higher daily charge
Keep 850 kWh and 30 days. Set the daily charge to $0.80.
Standing charge: $24.00
Subtotal: 76.50 + 24.00 = $100.50
Bill: $105.53
A mild 1,200 kWh winter month at the default $0.45 daily charge is $127.58. Usage still dominates once the boiler runs. The daily line is the whole bill when it does not.
Fig 6 · 1/2
A year that is not flat
Four summer months at 200 kWh, four default months, four winter months at 1,800 kWh
Cash spent
- Seasonal year
- Flat default
| Point | Seasonal year | Flat default |
|---|---|---|
| 0 mo | $0.00 | $0.00 |
| 4 mo | $132 | $378 |
| 8 mo | $510 | $756 |
| 12 mo | $1.2k | $1.1k |
After four summer months the total is $132.32.
The year closes at $1,247.44.
Four × 33.08 = 132.32. Four × 94.50 = 378.00, plus 132.32 = 510.32. Four × 184.28 = 737.12, plus 510.32 = 1,247.44.
The heat pump payback post is the next question after a winter like that. The electricity bill estimate is the same three-line shape on the other meter.
The ten bills next to each other
| Example | kWh | Rate | Daily $ | Days | Tax | Bill |
|---|---|---|---|---|---|---|
| 1. Defaults | 850 | $0.09 | 0.45 | 30 | 5% | $94.50 |
| 2. Winter | 1,800 | $0.09 | 0.45 | 30 | 5% | $184.28 |
| 3. Summer | 200 | $0.09 | 0.45 | 30 | 5% | $33.08 |
| 4. 31-day month | 850 | $0.09 | 0.45 | 31 | 5% | $94.97 |
| 4b. February | 850 | $0.09 | 0.45 | 28 | 5% | $93.55 |
| 5. Rate $0.12 | 850 | $0.12 | 0.45 | 30 | 5% | $121.28 |
| 6. No standing | 850 | $0.09 | 0.00 | 30 | 5% | $80.33 |
| 7. No tax | 850 | $0.09 | 0.45 | 30 | 0% | $90.00 |
| 8. Zero use | 0 | $0.09 | 0.45 | 30 | 5% | $14.18 |
| 9. 61-day bill | 1,700 | $0.09 | 0.45 | 61 | 5% | $189.47 |
| 10. Daily $0.80 | 850 | $0.09 | 0.80 | 30 | 5% | $105.53 |
Open the gas bill estimate calculator with the kWh (or therms converted to kWh), the unit rate, the daily standing charge, and the days on the statement. Compare a winter month with the heating system cost tool if you are choosing a boiler or a heat pump. The electric side of the same house is the electricity bill estimate.