Gas Cost Calculator
Enter the one-way distance, your car's miles per gallon and the gas price. Choose round trip to double the distance.
mi
mpg
$/gal
people
Default price: national average of $4.26/gal for regular (AAA, October 27, 2026, via Yahoo Finance).
Result–
Ways to cut fuel cost
- Keep tires inflated to the pressure on the driver's door sticker.
- Drive steadily: hard acceleration and high speeds use noticeably more fuel.
- Remove roof racks and extra weight when you don't need them.
- Compare prices along your route; fuel is often cheaper away from highway exits.
Your car's real-world MPG can differ from its sticker rating. For the most accurate cost, fill the tank, note the miles driven until the next fill, and divide.
Gas cost per 100 miles
| Fuel economy | Gallons per 100 mi | Cost at $4.26/gal |
|---|---|---|
| 15 mpg | 6.67 | $28.4 |
| 20 mpg | 5 | $21.3 |
| 25 mpg | 4 | $17.04 |
| 30 mpg | 3.33 | $14.2 |
| 35 mpg | 2.86 | $12.17 |
| 40 mpg | 2.5 | $10.65 |
| 50 mpg | 2 | $8.52 |
Fuel cost = miles ÷ mpg × price per gallon
Highway mpg is usually higher than the combined rating, so long interstate trips often cost a little less than estimated.
Questions
How much gas will a road trip take?
Divide the total miles by your car's mpg. A 700-mile round trip at 28 mpg needs 25 gallons.
How do I split gas money fairly?
Split the total fuel cost by the number of people riding, or by the miles each person was in the car.