Work it out from the miles, not the clock
If you know the drive in hours, turn it into miles first: gas depends on miles, and your map app shows both for the route.
Then divide the miles by the car’s fuel economy to get gallons, and multiply by the price per gallon. If you don’t know the car’s MPG, the EPA rating on FuelEconomy.gov is a fair starting point; the car’s trip computer is better if it has one.
The table below turns hours into miles at an average of 60 mph. That speed is an example to make the arithmetic visible, not an average for U.S. highways; city traffic and stops lower it.
| Driving time | Miles | Gallons | Gas for the car | Each of 2 | Each of 3 |
|---|---|---|---|---|---|
| 1 hour | 60 | 2 | $8.96 | $4.48 | $2.99 |
| 2 hours | 120 | 4 | $17.91 | $8.96 | $5.97 |
| 3 hours | 180 | 6 | $26.87 | $13.43 | $8.96 |
| 4 hours | 240 | 8 | $35.82 | $17.91 | $11.94 |
| 6 hours | 360 | 12 | $53.74 | $26.87 | $17.91 |
| 8 hours | 480 | 16 | $71.65 | $35.82 | $23.88 |
“Each of 2” and “Each of 3” split the gas among everyone in the car, driver included. One-way drives; a round trip doubles every amount.
Calculated with the same engine as the trip gas cost calculator. Replace the speed, MPG and price with your own.
Reference: EIA: Gasoline and Diesel Fuel Update · FuelEconomy.gov: Find and compare cars
Add tolls and parking before you split
Tolls and parking are part of the trip too. If your group shares them, add them to the total before you split. For the weekend trip above with three people and $12 in tolls, the total becomes $47.82, or $15.94 each instead of $11.94 for gas alone.
Keep food, lodging and tickets separate from gas money. Folding them in makes the number hard to check.
Should you pay the IRS mileage rate instead?
A per-mile rate such as the IRS standard mileage rate is a different measure. For July 1 to December 31, 2026, the IRS rates are 76 cents a mile for business use, 23.5 cents for medical or military moving purposes and 14 cents for charity.
Those are tax figures for those deductions, not what the gas for a trip costs. In the example car, gas alone comes to $0.1493 a mile ($4.478 ÷ 30 MPG). If your group wants to share the wear on the car as well, agree on it openly; the trip calculator counts gas, tolls and parking only.
Reference: IRS: Standard mileage rates
Receipts or the math?
On a long trip with several fill-ups, you can also fill the tank at the start and again at the end, add up the receipts from the trip, and split that. It measures the gas you actually bought, including detours and time spent idling.
The math is better before the drive, when you want to agree on a number, and for short rides with no fill-up at all. The two methods should land close if the MPG and price you enter are realistic.
Use the calculator with your numbers
The worked example below comes from the trip gas cost calculator’s engine. Change the miles, MPG, price and people to match your ride.
| Item | Example result |
|---|---|
| Miles driven | 240 miles |
| Gallons | 8 gallons |
| Gas for the car | $35.82 |
| Each of 3, driver included | $11.94 |
| Each of 2 passengers, driver not paying | $17.91 |
Authored example inputs, not a typical trip. Shares are rounded to the cent. Tolls and parking would be added to the gas before splitting.
Illustrative figures, not market averages. The underlying costs are calculated with the same engine as the tool; additional derived measures are labeled.
Split the gas for my drive ↗About this guide
Prepared by RealCostTools with AI-assisted research and drafting. Sources and calculations were checked September 27, 2026. Gas amounts use EIA’s U.S. regular gasoline average for the week of September 21, 2026, released September 22, 2026; every trip in this guide is an example, not a measurement of typical rides.
Sources and calculation notes
- EIA: Gasoline and Diesel Fuel Update
U.S. regular gasoline retail price, $4.478 a gallon for the week of September 21, 2026, released September 22, 2026; prices include all taxes. Checked September 27, 2026. A national weekly average, not the price at a station.
- IRS: Standard mileage rates
2026 rates for July 1 to December 31: 76 cents a mile for business, 23.5 cents for medical or military moving, 14 cents for charity (IR-2026-29); page updated July 28, 2026, checked September 27, 2026. Tax figures; not used as a gas cost.
- FuelEconomy.gov: Find and compare cars
EPA fuel economy ratings by year, make and model, checked September 27, 2026. A comparison rating; real MPG on a given drive differs.
- RealCostTools: trip gas cost methodology
The formulas behind every amount in this guide: miles ÷ MPG × price, plus tolls and parking, divided by the people paying.
Read the trip gas cost methodology for the model assumptions and excluded costs.
Published . Sources checked . Editorial policy · Corrections