CCalcanova
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Everyday

Fuel Cost Calculator

Work out what a trip costs in fuel from the distance, your vehicle's efficiency, and the price at the pump — in metric or imperial.

miles

Double it for a return journey

mpg

Real-world figures are usually worse than the official ones

USDper gallon
people

Optional — splits the total between everyone in the car

Fuel needed
10 gal
Cost per mile
$0.12
Total trip cost
$35.00

Fuel only — tolls, parking, and wear on the vehicle are not included. Gallons are US gallons (3.785 litres); a UK imperial gallon is about 20% larger, so convert before entering a UK mpg figure.

What a journey really costs in fuel

Fuel cost is three numbers multiplied together: how far you are going, how much fuel your vehicle uses over that distance, and what that fuel costs. The only complication is units, because the world measures efficiency in three incompatible ways. Pick the combination that matches your dashboard and your local pump — miles per US gallon, litres per 100 km, or kilometres per litre — and the conversion is handled for you.

Reading the three efficiency systems

Miles per gallon and kilometres per litre measure distance travelled per unit of fuel, so higher is better. Litres per 100 km, the standard across Europe and much of Asia, measures fuel consumed per fixed distance, so lower is better. The two styles are reciprocals of each other, which is why a car that looks twice as efficient on one scale rarely looks twice as efficient on the other.

Comparing driving with the alternatives

The cost-per-distance figure is what makes this useful beyond a single trip: it turns your vehicle into a simple rate you can multiply by any journey, compare against a train fare, or use to price a mileage reimbursement. Remember that fuel is only part of the true cost of driving — tyres, servicing, depreciation, tolls, and parking are all real — and that splitting the total between passengers changes the picture completely for longer trips.

Frequently asked questions

+How do I calculate the fuel cost of a trip?

Work out how much fuel the trip uses, then multiply by the pump price. With mpg or km/L, fuel used is distance ÷ efficiency; with L/100 km it is distance × efficiency ÷ 100. A 300 mile trip at 30 mpg needs 10 gallons, which at 3.50 a gallon costs 35.

+How do I convert between mpg and L/100 km?

They are inversely related: L/100 km = 235.2 ÷ mpg (US), and the same formula converts back the other way. So 30 mpg is about 7.8 L/100 km, and 8 L/100 km is about 29 mpg. Note that a lower L/100 km figure is better, while a higher mpg figure is better.

+Are US and UK gallons the same?

No — a US gallon is 3.785 litres and a UK imperial gallon is 4.546 litres, about 20% larger. A car rated at 40 mpg in the UK is roughly 33 mpg by US measure. This calculator uses US gallons, so convert a UK figure by multiplying it by 0.833 first.

+Why does my real fuel consumption differ from the official rating?

Official figures come from standardised test cycles. Cold weather, short journeys, heavy loads, roof boxes, air conditioning, under-inflated tyres, and sustained high speeds all push real consumption higher — often 10–25% above the sticker. For a realistic budget, use the figure from your own trip computer or from dividing your recent distances by the fuel you actually bought.

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