Should I use the mpg on the window sticker?

Use the number your own car shows over a full tank if you have it. EPA combined figures are a fair starting point, but a loaded car on a highway at 75 mph with a roof box does not return the combined figure — and the gap is usually 10–20 %, which is the difference between this estimate and your actual receipts.

Does air conditioning or a roof box really matter?

Enough to notice on a long drive. A roof box or bikes on the roof cost fuel at highway speed because drag rises with the square of speed; air conditioning costs a little at any speed. If you are carrying something on the roof, take a few mpg off the figure you enter rather than adding a margin at the end.

Why does the tool ask how many people are travelling?

Because the number people actually want is the one they will ask each other for. Fuel is the one shared cost of a road trip that everybody agrees to split, and the per-person figure is what ends up in the message you send the others.

Round trip or one way?

Enter the one-way distance and tick the round-trip box. The tool doubles the distance rather than asking you to, which is the arithmetic most often forgotten when people estimate a trip in their head.

Fuel Cost Calculator — Gas for a Road Trip

Fuel cost calculator

A 1,200-mile drive there and back in a car doing 28 mpg, with gas at $4.30 a gallon, costs $368.58 of fuel — $184.29 each if two of you are splitting it.

Result$368.58

$368.58 of fuel — $184.29 each with 2 of you in the car.

Trip Card

This trip only: the numbers it produced, the limits and tariffs it was checked against, and when those were checked. Print it or send it to whoever is travelling with you.

Distance driven	2,400 mi
Consumption	28 mpg (US)
Fuel needed	85.8 gal
Fuel cost	$368.58
Per person	$184.29

Trip Card generated on September 20, 2026

Four inputs, one bill

Distance, fuel economy, pump price and how many of you there are. The tool converts whatever units you use into a single basis internally — miles or kilometres, mpg or litres per 100 km, price per gallon or per litre — so you can enter what you have in front of you rather than converting first.

Switching a unit converts the value you already typed instead of clearing it. A price of $4.30 a gallon becomes $1.14 a litre, not an empty box.

Why the total rounds up

Money rounds up to the cent here, never down. An estimate that is optimistic about fuel is the one failure of this calculator that costs a real person real money at the far end of a drive, and the difference between rounding directions is a few cents against the risk of being short.

The number you can hand over

The result carries a per-person split and the volume of fuel the trip needs — useful when the trip needs more gallons than the tank holds several times over, because that is a series of stops rather than one. The Trip Card holds those figures with the price they were computed from, so when somebody asks why they owe $184.29, the answer is on the card rather than in your memory.

What this means in United States

Gas is priced per US gallon, and state taxes move the pump price by more than a dollar between, say, Texas and California, so the field starts from the national average rather than a local one. Change it to the price you actually saw.

Questions people actually ask

Should I use the mpg on the window sticker?: Use the number your own car shows over a full tank if you have it. EPA combined figures are a fair starting point, but a loaded car on a highway at 75 mph with a roof box does not return the combined figure — and the gap is usually 10–20 %, which is the difference between this estimate and your actual receipts.
Does air conditioning or a roof box really matter?: Enough to notice on a long drive. A roof box or bikes on the roof cost fuel at highway speed because drag rises with the square of speed; air conditioning costs a little at any speed. If you are carrying something on the roof, take a few mpg off the figure you enter rather than adding a margin at the end.
Why does the tool ask how many people are travelling?: Because the number people actually want is the one they will ask each other for. Fuel is the one shared cost of a road trip that everybody agrees to split, and the per-person figure is what ends up in the message you send the others.
Round trip or one way?: Enter the one-way distance and tick the round-trip box. The tool doubles the distance rather than asking you to, which is the arithmetic most often forgotten when people estimate a trip in their head.

Where these numbers come from

Last checked: September 19, 2026

US national average pump price, regular unleaded, mid-September 2026 (unverified starting figure) — September 19, 2026

In the United States baggage allowances are the carrier's own contract of carriage; the Department of Transportation requires the fees to be published, not harmonised, so two airlines on the same route can measure the same suitcase differently.

These figures are guidance, not a quotation. Airline allowances, gate fees and toll tariffs change; check the carrier or the road operator before you travel.