Fuel Cost Calculator

Planning a trip or tracking your commute? Enter distance, your car's average and today's fuel price — get litres needed, total cost and cost per kilometer.

The math, and how to lower it

Litres = distance ÷ average, and cost = litres × price. A 350 km trip in a car doing 14 km/l with fuel at 280/litre needs 25 litres → 7,000. Knowing your cost per km makes decisions easy: comparing bike vs car, whether a cheaper bazaar across town is really cheaper, or what to charge a friend for a shared ride. To improve your average: correct tyre pressure, gentle acceleration, less idling and a clean air filter — typically worth 10–20% together.

Petrol, diesel and CNG

Fuel type changes both price and efficiency. Diesel engines usually deliver more kilometres per litre than petrol, and CNG is often cheaper per kilometre but gives less range and needs space for a cylinder. To compare fairly, work out the cost per kilometre for each option — which is exactly what this calculator gives you — rather than comparing fuel prices alone.

Budgeting a trip

Once you know your car's average and the current fuel price, you can budget any journey in seconds and plan refuelling stops. For a monthly commute, multiply the one-way cost by your number of trips to see the true running cost — often an eye-opening figure that helps when deciding between driving, carpooling or public transport.

Converting between fuel-economy units

Countries measure efficiency in incompatible ways, which makes comparing cars across markets confusing. km/L and mpg are "distance per fuel" — higher is better. L/100km is "fuel per distance" — lower is better, and it runs in the opposite direction.

The conversions: L/100km = 100 ÷ km/L, so 14 km/L is 7.1 L/100km. For miles per gallon, note the US and Imperial gallon differ — km/L × 2.352 = US mpg, while km/L × 2.825 = Imperial mpg. A car doing 14 km/L is 33 US mpg but 39.5 Imperial mpg. The same vehicle, two very different-sounding figures, which is why UK and US reviews of the same model rarely agree.

Why your real economy is worse than the sticker

Manufacturer figures come from controlled tests, and real-world driving is typically 10–25% worse. The main causes are worth knowing because most are within your control:

• Speed — drag rises with the square of velocity. Above roughly 90 km/h economy falls away sharply; 120 km/h can cost 20% versus 100 km/h.
• Stop-start traffic — every acceleration from rest is expensive, which is why city figures trail highway ones.
• Tyre pressure — under-inflation adds rolling resistance and can cost 3%.
• Air conditioning — up to 10% in heat, though at highway speed it beats open windows.
• Weight and roof boxes — a roof rack can cost 10–15% from drag alone, even empty.
• Short trips — a cold engine runs rich; the first few kilometres are the least efficient you will drive.

Working out cost per kilometre

Cost per km is the figure that makes decisions easy — comparing driving with public transport, setting a fair rate for shared trips, or invoicing mileage. It is simply fuel price ÷ economy.

At 280 per litre and 14 km/L, that is 20 per kilometre, so a 60 km round trip costs 1,200 in fuel. Bear in mind that is fuel only. The true cost of running a car also includes servicing, tyres, insurance and depreciation, which together often match or exceed fuel. If you are deciding whether a journey is worth driving, roughly doubling the fuel figure gives a more honest comparison.

Frequently asked questions