Fuel Cost Calculator
Work out the fuel cost of a trip from distance, efficiency and fuel price.
Results update as you type.
About this calculator
A fuel cost calculator estimates what a journey costs in fuel from three numbers: the distance, your vehicle’s fuel efficiency and the price of fuel. In mpg mode it divides the distance by your miles-per-gallon to get gallons used, then multiplies by the price per gallon. In metric mode it multiplies distance ÷ 100 by your litres-per-100km figure to get litres, then multiplies by the price per litre.
For example, a 300-mile trip in a car doing 30 mpg with fuel at 3.50 a gallon uses 300 ÷ 30 = 10 gallons, costing 10 × 3.50 = 35. Split between two people under advanced options, that is 17.50 each.
Use it to budget a road trip, compare the running cost of two vehicles, decide whether to drive or take the train, or work out a fair share for carpoolers. Because real mileage varies with speed, load, traffic and terrain, treat the result as a solid estimate based on the efficiency figure you enter.
Frequently asked questions
How is trip fuel cost calculated?
In mpg mode: fuel used = distance / mpg, then cost = fuel x price per gallon. In metric mode: litres = distance / 100 x (l/100km), then cost = litres x price per litre.
Does driving style change the result?
Yes. Real efficiency varies with speed, traffic, load and terrain, so treat this as an estimate based on your entered efficiency figure.
How do I switch between mpg and litres per 100 km?
Use the units setting under advanced options. Miles & mpg treats distance in miles and efficiency as miles per gallon; km & l/100km treats distance in kilometres and efficiency as litres per 100 km, with the price read per litre.
How do I split fuel cost between passengers?
Set the number of people under advanced options. The calculator divides the total trip fuel cost evenly, so each traveller sees their share — useful for carpools and shared road trips.
How much fuel will my trip use?
The calculator shows the fuel used as well as the cost. In mpg mode it is distance ÷ mpg (gallons); in metric mode it is distance ÷ 100 × l/100km (litres). A 300-mile trip at 30 mpg uses 10 gallons.
How can I estimate a round trip?
Enter the total distance for both legs, or double a one-way figure. Since cost rises directly with distance, a round trip simply costs twice a one-way trip at the same efficiency and fuel price.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/fuel-cost/curl
curl "https://calculator.free/api/v1/fuel-cost/?distance=300&efficiency=30&price=3.5"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/fuel-cost/?" + new URLSearchParams({
"distance": "300",
"efficiency": "30",
"price": "3.5"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.