Gas Cost Calculator for a Trip
Planning a road trip? This gas travel cost calculator works out how many gallons you'll burn and what they will cost, using miles, MPG and the latest US average price per gallon. Add passengers to see what each person owes.
Your trip
Your car & gas price
Sharing & extras optional
Same trip with a different car
How to figure out the cost of gas for a trip
Divide the miles you will drive by your car's MPG to get the gallons you need, then multiply by the price per gallon:
For example, a 450-mile road trip in an SUV that gets 24 MPG needs 18.75 gallons. At the national average of $4.23 a gallon (29 October 2026), the gas costs about $79.24. Drive back as well and it doubles to $158.48.
Gas cost per 100 miles by MPG
At $4.23 per gallon for regular gas and $6.35 for diesel:
| Fuel economy | Gallons per 100 mi | Gas cost per 100 mi | 500-mile trip | 1,000-mile trip |
|---|---|---|---|---|
| 15 MPG | 6.7 | $28.17 | $140.87 | $281.73 |
| 20 MPG | 5.0 | $21.13 | $105.65 | $211.30 |
| 25 MPG | 4.0 | $16.90 | $84.52 | $169.04 |
| 30 MPG | 3.3 | $14.09 | $70.43 | $140.87 |
| 35 MPG | 2.9 | $12.07 | $60.37 | $120.74 |
| 40 MPG | 2.5 | $10.57 | $52.83 | $105.65 |
| 50 MPG | 2.0 | $8.45 | $42.26 | $84.52 |
Getting the numbers right
- Miles: take the driving distance from your map app. Add a little for detours, finding parking and driving around at your destination.
- MPG: use the average your car's trip computer shows, or the EPA "combined" MPG from fueleconomy.gov. Highway driving at steady speed is often better than combined; towing, roof boxes and mountain roads are worse.
- Price per gallon: the calculator starts with the national average for regular or diesel. Prices differ a lot between states, so put in what your local stations charge, or the price along your route.
Driving abroad?
Outside the US, fuel is sold by the litre and economy is often given in liters per 100 km. Choose the country in the calculator and it switches to kilometers, L/100 km and the local currency, converting what you have already entered. For trips in Britain, see the UK petrol cost calculator.