How can I split fuel costs for a road trip?

Divide the total fuel cost by the number of people sharing the ride. Enter the number of passengers and the calculator shows the cost per person.

Should I use city, highway, or combined MPG for a road trip estimate?

Use highway MPG if the trip is mostly highway driving, which most road trips are, since it's typically higher than the combined or city figure and gives a more accurate cost estimate for that kind of driving.

Fuel Cost Calculator

Q: How do I calculate the fuel cost of a trip?

Divide the trip distance by your vehicle's MPG to get gallons used, then multiply by the price per gallon. A 300-mile trip in a 30 MPG car at $3.50/gallon uses 10 gallons and costs $35.

Q: Does this work for a round trip?

Enter the total distance you'll drive. For a round trip, double the one-way distance before entering it, or enter the round-trip figure directly.

Q: How much does fuel economy actually affect trip cost?

Significantly — a 500-mile trip costs $87.50 at 20 MPG but just $43.75 at 40 MPG with gas at $3.50 a gallon, exactly half, because the gallons used scales inversely with MPG.

Find the fuel cost of any trip from the distance, your vehicle's fuel economy, and the price of gas — and split it across passengers.

Written by the Calculator Index team · Last reviewed September 2026

Total fuel cost

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Fuel used

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Cost per person

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Cost per mile

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The fuel cost formula

Gallons = Distance ÷ MPG
Cost = Gallons × Price per gallon · Per person = Cost ÷ people

Worked example

A 300-mile trip in a 30 MPG car at $3.50/gal: 300 ÷ 30 = 10 gallons × $3.50 = $35. Split 4 ways = $8.75 each.

Worked example — metric road trip

An 800 km trip in a car that uses 6 L/100km, fuel at $1.55/litre: 800 × 6 ÷ 100 = 48 litres × $1.55 = $74.40 total; split 3 ways ≈ $24.80 each.

Planning trips and comparing vehicles

Fuel is often the biggest variable cost of a road trip, and this makes it concrete. It's also useful for comparing vehicles: the same 300-mile trip costs $35 at 30 MPG but $52.50 at 20 MPG — a difference that compounds over a year of driving. The calculator handles metric too (L/100km and price per litre). For the flip side — measuring your car's actual MPG from fill-ups — use the gas mileage calculator, and for a car purchase's total cost, the auto loan calculator.

Cost impact of fuel economy on a 500-mile trip

MPG	Gallons used	Cost at $3.50/gal
20	25.0	$87.50
25	20.0	$70.00
30	16.7	$58.33
35	14.3	$50.00
40	12.5	$43.75

Common fuel cost estimation mistakes

Entering a one-way distance when a round trip was intended, or vice versa. The calculator uses whatever distance is entered — double a one-way distance yourself for a round trip, and don't double a figure that's already round-trip.
Using an inconsistent fuel price across comparisons. Use the same all-in price you'd actually pay at the pump for every scenario being compared, rather than mixing a rough estimate with an exact receipt total.
Ignoring that fuel economy is highway- vs. city-dependent. If a trip is mostly highway, use your vehicle's highway MPG rather than combined or city MPG — the resulting cost estimate can otherwise be off by 15-20%.

Frequently asked questions

How do I calculate the fuel cost of a trip?

Distance ÷ MPG = gallons; × price per gallon = cost. 300 mi at 30 MPG, $3.50/gal = $35.

How can I split fuel costs?

Divide total cost by the number of people — enter passengers to see per-person cost.

Does this work for a round trip?

Yes — enter the total (round-trip) distance.

How much does fuel economy actually affect trip cost?

A lot — a 500-mile trip costs $87.50 at 20 MPG but just $43.75 at 40 MPG, exactly half, since gallons used scales inversely with MPG.

Should I use city, highway, or combined MPG?

Use highway MPG for mostly-highway road trips — it's usually higher than combined or city figures and gives a more accurate estimate.

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Last reviewed: September 2026.