Fuel Cost Calculator — cost of a trip

How it works

The cost of fuel for a trip has two steps: work out how much fuel you will burn, then multiply by the price. The fuel used is the distance divided by your vehicle's fuel economy, which gives:

cost = (distance ÷ MPG) × price per gallon

This is the method the EPA uses for the "annual fuel cost" figure on new-car labels — estimated miles divided by the vehicle's MPG, times the fuel price. Enter the trip distance, your fuel economy in miles per gallon, and the price per gallon.

Keep the units consistent: with miles, MPG and dollars per gallon you get dollars. The same structure works for kilometres, km/L and price per litre — just make sure the distance, economy and price all use the same units.

Worked example

A 300-mile trip at 30 MPG with fuel at $3.70/gallon uses 300 ÷ 30 = 10 gallons, costing 10 × 3.70 = $37.00. A short 40-mile commute at 28 MPG and $3.50 costs about $5.00; a 1000-mile road trip at 32 MPG and $3.70 runs to $115.63; and a thirsty vehicle doing 300 miles at just 15 MPG with $4.00 fuel costs $80.00 — more than double the efficient case.

Frequently asked questions

How do I calculate the fuel cost of a trip?

Divide the trip distance by your fuel economy (MPG) to get the gallons needed, then multiply by the price per gallon: cost = (distance ÷ MPG) × price. This is the same method behind the EPA's annual-fuel-cost estimates.

What fuel economy (MPG) should I use?

Use your real-world MPG if you know it — calculate it from a few fill-ups for the best accuracy. Otherwise use the EPA combined rating from the window sticker, keeping in mind that actual mileage is often a little lower than the rating.

How does fuel economy affect the cost?

Cost is inversely proportional to MPG: at twice the fuel economy, a trip costs half as much. That is why a 15 MPG truck can cost double a 30 MPG car for the same distance, even before differences in fuel grade.

Can I use this for a round trip?

Yes — just enter the total distance for both legs. For a round trip, double the one-way distance before entering it, or add up all the miles you expect to drive.

Does this work outside the US, with litres and kilometres?

Yes. The formula only needs distance, fuel economy and price in matching units. Enter kilometres, km/L and price per litre to get the cost in your currency. If your fuel economy is in litres per 100 km instead, convert it to km/L first (or use a consumption-based calculator).

Why is my actual trip cost different?

Real fuel use varies with speed, traffic, terrain, weather, cargo and driving style, and pump prices change constantly. Treat the result as a solid estimate based on your average MPG and the price you enter, not an exact figure.