Fuel Cost Calculator

Estimate how much gas a drive will take and what it will cost, for one way or the round trip, and what each person owes if you split it.

Your real-world MPG, or the EPA highway figure for a mostly-highway trip.

$3.50 is only an example. Use the price where you'll fill up; EIA publishes weekly national and regional averages.

Fuel cost
$31.25
Gallons needed
8.93
Total miles
250
Fuel cost per mile
12.5 cents
  • Based on $3.50 a gallon. Prices vary by region and week; city driving, mountains, heavy loads and high speeds usually mean lower MPG than the rating.

If gas costs more or less

Price per gallonFuel cost
$3.00$26.79
$3.25$29.02
$3.50$31.25
$3.75$33.48
$4.00$35.71

How trip fuel cost is calculated

Divide the distance by your car's miles per gallon to get the gallons you'll burn, then multiply by the price per gallon. A 250-mile drive in a car that gets 28 MPG uses about 8.93 gallons; at $3.50 a gallon that's $31.25.

Another way to see it is cost per mile: price divided by MPG. At $3.50 and 28 MPG, every mile costs 12.5 cents in fuel, so any distance times $0.125 gives the fuel cost.

Getting the inputs right

Distance: use the route distance from a map app, not the straight-line distance, and add a little for detours, finding parking and side trips.

Fuel economy: your own measured MPG is best (the gas mileage calculator works it out from a fill-up). If you don't know it, the EPA highway figure for your model on FuelEconomy.gov is a reasonable start for an interstate trip, and the city figure for local driving. A loaded car, a roof box, mountains or sustained high speeds will pull real MPG below the rating.

Gas price: prices differ by state and change week to week. The U.S. Energy Information Administration publishes weekly average retail prices for the country, regions and some states and cities; use the region you'll be driving through, or check prices along the route.

Splitting gas with passengers

Dividing the fuel cost equally is the usual approach for a shared trip. Some groups also chip in toward tolls and parking, or the driver's wear and tear; fuel is only part of the cost of driving, and the cost per mile calculator shows the rest.

The formula

Gallons = D ÷ MPGFuel cost = Gallons × PPer person = Fuel cost ÷ N
  • D = total miles (double the one-way distance for a round trip)
  • MPG = fuel economy in miles per gallon
  • P = price per gallon
  • N = number of people splitting the cost

Example

  1. A 250-mile drive each way in a car that averages 28 MPG, with gas at an example price of $3.50 a gallon.
  2. One way: 250 ÷ 28 = 8.93 gallons, × $3.50 = $31.25.
  3. Round trip: 500 miles ÷ 28 = 17.86 gallons, × $3.50 = $62.50.
  4. Split between two people, each pays $31.25.
  5. If gas were $0.50 higher ($4.00), the round trip would cost $71.43.

Frequently asked questions

How much gas will a 100-mile trip use?

Divide 100 by your MPG. At 25 MPG it's 4 gallons; at 40 MPG it's 2.5 gallons. Multiply by the price per gallon for the cost.

Where can I find current gas prices?

The U.S. Energy Information Administration (EIA) publishes average retail gasoline and diesel prices every week, nationally and by region. Gas station apps and map apps show prices at individual stations.

Should I use city or highway MPG?

Use highway MPG for long interstate drives and city MPG for local driving. For a mix, use the combined figure, or better, your own measured MPG.

Does driving faster use more gas?

Usually, yes. FuelEconomy.gov says gas mileage generally drops quickly above 50 mph, and that slowing down by 5 to 10 mph on the highway can improve fuel economy by 7% to 14%.

How do I work out fuel cost for an electric car?

Use the same idea with electricity: miles ÷ miles per kWh × price per kWh. This calculator is set up for gallons and MPG.

Sources

Last reviewed for 2026. How we calculate.