Trip fuel and money: distance × consumption × pump price.
Costs are estimates: real-world consumption depends on speed, traffic, payload and weather.
The fuel cost of a trip used to be the kind of number you estimated on the back of an envelope and rounded up by ten percent for safety. Two changes pushed it onto every dashboard in the past decade: pump prices became wildly volatile (between 2020 and 2023 the price of a litre of diesel in France swung from €1.20 to €2.20 and back), and remote work made it normal for the same household to drive between two cities each week, multiplying small per-kilometre differences into significant monthly bills. Fuel cost is also one of the simplest and most actionable comparisons between vehicles: a car that consumes 4 L/100 km versus one that consumes 7 L/100 km is a 75 % difference in fuel bills for identical use, dwarfing most other ownership costs short of insurance. This calculator turns three numbers — trip distance, vehicle consumption, and pump price — into a total cost and a per-kilometre figure, in metric or imperial units, with the visitor's local currency auto-detected from the browser locale.
Fuel cost is the product of three quantities expressed in compatible units. Litres used = distance (km) ÷ 100 × consumption (L/100 km). Total cost = litres used × price per litre. From those two, two derived figures are useful: cost per kilometre = total cost / distance, and cost per 100 km = cost per kilometre × 100. The unit toggles handle the conversions internally: kilometres convert to miles by × 0.6214 (or miles to km by × 1.6093); litres per 100 km convert to miles per gallon (US) via the inverse relation MPG = 235.215 / (L/100 km), and back via L/100 km = 235.215 / MPG; price per US gallon converts to price per litre by ÷ 3.7854. So whether you enter "500 km, 6.5 L/100 km, €1.85/L" or "310 mi, 36 MPG, $4.20/gal", the calculator works in metric internally and converts only for display, which avoids accumulated rounding.
Three input groups: distance with a km/miles toggle, consumption with three unit options (L/100 km, km/L, MPG US), and pump price with a per-litre or per-US-gallon toggle. The defaults — 500 km, 6.5 L/100 km, €1.85/L — represent a typical Paris-to-Lyon round trip with a small Renault and current French diesel prices. The result panel shows total trip cost as the headline KPI, the litres consumed alongside, the cost per 100 km for comparison with other vehicles or other trips, and the effective price per litre after unit conversion (so you can sanity-check that an MPG-and-per-gallon entry was interpreted correctly).
A daily commuter drives 60 km round trip in a hybrid that averages 5.0 L/100 km, with diesel at €1.85/L: 60 × 5 / 100 = 3 litres per day, × €1.85 = €5.55 per day, ≈ €115/month over twenty-one working days. Compare to a 7.5 L/100 km mid-size petrol car at €1.95/L: 60 × 7.5 / 100 × 1.95 = €8.78 per day, ≈ €184/month — a €69/month delta or roughly €830/year purely from fuel efficiency. A US road-trip example: 800 miles in a 32-MPG car at $3.95/gal: 800 / 32 = 25 gallons, × 3.95 = $98.75 for the trip. A French summer drive of 1 200 km in a Tesla — switch to 0 L/100 km is not supported here; the calculator is for combustion vehicles. For an electric equivalent, the comparison would replace L/100 km with kWh/100 km and pump price with electricity price; the math is the same shape but the unit conversions differ.
First, mixing imperial and metric mid-stream. UK MPG (imperial gallons) and US MPG (US gallons) differ by 20 % — a US 30 MPG is a UK 36 MPG. This calculator uses the US gallon convention. Second, taking the manufacturer-quoted consumption at face value. The WLTP cycle (used in Europe since 2017) is more realistic than the older NEDC cycle but still understates real-world consumption by about 15 to 25 % for petrol and 10 to 15 % for diesel — drivers should add a margin to the brochure number. Third, ignoring tolls. On a 600 km autoroute trip in France, tolls can run €40 to €60, often more than the fuel cost itself for a small car. Fourth, using last week's price when refilling next week. Pump prices move several cents per litre per week and the right input is the price you expect to pay, not last month's average. Fifth, forgetting that consumption is non-linear in speed. Above 110 km/h, fuel consumption rises sharply (drag scales with the square of speed), so a 130-km/h motorway trip can consume 30 % more than a 100-km/h national-road trip of the same distance — adjust the L/100 km input accordingly.
Fuel cost is the heart of the total cost of ownership comparison every car buyer eventually does. Add insurance (typically €500–€1 500/year for an average car in Europe), depreciation (the largest line item for new cars in their first three years), maintenance, registration tax, and tolls/parking, and the fuel-only number is rarely more than a third of the total. For ride-share economics, the relevant figure is cost per kilometre after the pump price — drivers paid by the kilometre need to know what cost they incur per kilometre to compare with the fare. For electric vehicles, swap litres for kilowatt-hours and pump price for electricity tariff: a 16 kWh/100 km EV at €0.20/kWh runs at €3.20 per 100 km, versus our default petrol example at €12.03/100 km — a 4× difference. For corporate fleets, the relevant calculation often inverts: given a fixed monthly fuel budget, how many kilometres can each driver still allocate? Same three-variable equation, solved for distance instead of cost.