A fuel cost calculator estimates how much gas a trip will use and what it will cost, based on the distance, your vehicle’s fuel economy and the price of fuel. Formula: Gallons = distance / MPG. Cost = gallons x price. A 300-mile trip at 28 mpg and $3.50 a gallon costs $37.50.
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How to use the fuel cost calculator
- Enter the trip distance in miles.
- Enter your vehicle’s fuel economy in mpg.
- Enter the price per gallon.
- Read the gallons used and the total fuel cost.
What is the fuel cost formula?
The fuel cost calculator divides the trip distance by your vehicle’s fuel economy to find how many gallons you will burn, then multiplies by the price per gallon:
- Gallons = miles ÷ miles per gallon (mpg)
- Fuel cost = gallons × price per gallon
Fuel cost calculator worked example
A 300-mile trip in a car that gets 28 mpg uses 300 ÷ 28 = 10.7 gallons. At $3.50 a gallon, that costs $37.50. At the U.S. average regular gasoline price of $4.284 per gallon reported by the U.S. Energy Information Administration for October 19, 2026, the same trip costs about $45.90.
Cost of a 300-mile trip by fuel economy
At $4.284 per gallon:
| MPG | Gallons | Fuel cost |
|---|---|---|
| 15 | 20.0 | $85.68 |
| 20 | 15.0 | $64.26 |
| 25 | 12.0 | $51.41 |
| 28 | 10.7 | $45.90 |
| 35 | 8.6 | $36.72 |
| 50 | 6.0 | $25.70 |
Fuel economy has a large effect: the 15-mpg vehicle spends more than three times as much as the 50-mpg hybrid on the same trip.
Round trips and commutes
Double the distance for a round trip. For a commute, multiply the daily round-trip miles by the number of workdays: a 30-mile round trip, 21 days a month, is 630 miles. At 28 mpg and $4.284, that is about $96 a month. If you share the drive, divide the total by the number of people.
Finding your real mpg
EPA ratings on the window sticker and on FuelEconomy.gov are a good starting point, but real-world mileage depends on speed, traffic, weather, load and maintenance. To measure your own, fill the tank, reset the trip meter, drive normally, refill and divide the miles by the gallons added. Highway trips usually get better mileage than city driving, so use the highway rating for long trips and the combined rating otherwise.
Fuel prices
Gasoline prices change weekly and vary a lot by region. EIA publishes weekly average retail prices for the U.S. and several regions. Enter the price you expect to pay along your route; if you will fill up in several states, use an average. For diesel vehicles, enter the diesel price and the vehicle’s diesel mpg.
Ways to spend less on fuel
- Drive at moderate highway speeds; mileage usually drops quickly above about 50 mph.
- Accelerate and brake gently.
- Keep tires inflated to the recommended pressure.
- Remove roof racks and extra weight you do not need.
- Combine errands into one trip.
Run the fuel cost calculator with different mpg values to see what a more efficient car or a change in driving habits would save each year.
Electric vehicles
For an electric vehicle, the same idea applies with electricity: divide miles by miles per kWh and multiply by your electricity rate. A car that goes 3.5 miles per kWh uses about 86 kWh for 300 miles; at 18¢ per kWh, that is about $15. The fuel cost calculator is built for gallons, so convert first.
Budgeting fuel for a road trip
For a long trip, plan with a little cushion. Detours, traffic, idling and air conditioning all add fuel, so many drivers add about 10% to the estimate. A 1,200-mile vacation at 25 mpg uses 48 gallons, or about $206 at $4.284 a gallon; with a 10% cushion, budget about $226. Towing or carrying a full load can lower mileage far more, so use a lower mpg in the fuel cost calculator for those trips. If you are comparing driving with flying or taking the train, add parking, tolls and wear on the car, not just the fuel cost calculator result.
Related converters and calculators
Related calculators:
- Gas mileage calculator: mpg
- Electricity calculator: EV charging
- Budget calculator: budget
- Speed calculator: travel time
Sources
U.S. EIA: Gasoline and Diesel Fuel Update; U.S. DOE/EPA FuelEconomy.gov: Fuel economy information.
Questions about this calculator
How do I calculate fuel cost?
Divide miles by mpg, then multiply by the price per gallon.
What does a 300-mile trip cost?
About $37.50 at 28 mpg and $3.50 a gallon.
What is the U.S. average gas price?
$4.284 per gallon for regular on October 19, 2026, per the EIA.
Should I use city or highway mpg?
Highway for long trips, combined for mixed driving.
How do I cost a round trip?
Double the distance.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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