Fuel Cost Calculator
What a trip costs in fuel: from distance, economy and pump price, split between passengers.
The trip
people in the car
This works out what a journey costs in fuel. Enter the distance, your vehicle's economy and the fuel price, and it returns the total cost and the cost per mile.
It can double the distance for a round trip and split the total between passengers, which is usually the number people are actually after.
What a journey costs in fuel
Fuel cost comes down to three numbers: how far you are going, how much fuel your vehicle uses to cover that distance, and what the fuel costs.
The middle one is where people go wrong. Using the manufacturer's figure rather than your own real economy can understate a trip by 10 to 20%, because official numbers come from test cycles rather than real roads.
Work out your real MPG first with the gas mileage calculator, then use it here. It takes one tank and makes every estimate afterwards honest.
Divide first, then multiply. Distance ÷ MPG gives the gallons you will burn; multiplying by the price turns that into money.
What to enter
- Distance
- One way. Tick the round trip box rather than doubling it yourself, so the split calculation still works correctly.
- Round trip
- Doubles the distance to count the drive home. Easy to forget, and it doubles the cost.
- Fuel economy
- MPG or L/100km. Use your own measured figure rather than the sticker for a realistic answer.
- Splitting between
- Number of people sharing the cost. Returns the per-person share.
- Tank size
- Optional. Used to show how many fill-ups the trip will need, which matters on long drives.
What this assumes
Fuel economy is steady for the whole trip. Motorway driving usually beats your average; heavy traffic and mountains do not.
Fuel price is constant. On a long trip across states it will not be, since fuel taxes vary considerably.
Only fuel is counted. Tolls, parking and the wear-and-tear cost of driving are not included.
How to calculate the fuel cost of a trip
Two steps: work out the gallons, then price them.
- distance ÷ MPG
- The gallons the trip will use
- × price
- Turns gallons into money
Get the total distance. Remember the return leg if you are coming back.
Divide by your MPG. That gives the gallons needed.
Multiply by the price. Use a realistic local price rather than the cheapest station you have ever seen.
Divide between passengers. If you are sharing, split the total by the number of people.
See a worked example: a 300-mile drive each way, 30 MPG, $3.50 a gallon, four people
- Distance
- 300 miles each way
- Economy
- 30 MPG
- Fuel price
- $3.50 per gallon
Round trip: 300 × 2 = 600 miles.
Gallons: 600 ÷ 30 = 20 gallons.
Cost: 20 × $3.50 = $70.
Split four ways: $70 ÷ 4 = $17.50 each.
Cost per mile is about 11.7 cents, which is a useful figure to keep for comparing journeys.
$70 total, or $17.50 each
Frequently asked questions
Divide the fuel price by your MPG. At $3.50 a gallon and 30 MPG that is about 11.7 cents a mile.
It is the most useful single number for comparing journeys or deciding whether a trip is worth making, because it does not depend on the length.
Only as a rough guide. Official figures come from standardised test cycles and are typically 10 to 20% better than real-world driving.
Measure a tank yourself with the gas mileage calculator and use that. It makes every estimate afterwards honest.
The usual approach is to divide the total fuel cost by everyone travelling, including the driver, since the driver is also going.
Some groups exclude the driver to account for wear on their car. Either is reasonable, but agree it before setting off rather than at the last petrol station.
Usually yes, above about 50 mph. Air resistance rises with the square of speed, so pushing through it takes disproportionately more fuel the faster you go.
Dropping from 75 to 65 mph typically saves around 10%, which on a 600-mile trip is roughly $7. Steady speed matters as much as the speed itself.
For a full car over moderate distances, driving usually wins because the fuel cost splits between everyone while airfares do not.
The comparison shifts once you add hotels for overnight stops, parking, and the value of the time. Work out the fuel cost here, then add those before deciding.
Problems people actually run into
Forgetting the return journey
Quoting a trip at the one-way distance halves the real cost, and it happens constantly when people are splitting money with friends.
Enter the one-way distance and tick round trip, rather than doubling the number yourself, so the per-person split stays correct.
Treating fuel as the whole cost of driving
Fuel is the visible cost, but tyres, servicing, depreciation and insurance all accrue per mile too. Official mileage reimbursement rates are several times the fuel cost alone for exactly that reason.
For a trip you are taking anyway, fuel is the right number. For deciding whether driving is genuinely cheaper than the alternative, it understates things considerably.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Last updated: September 3, 2026