Fuel Cost Calculator: Estimate Trip Fuel and Cost

Calculate your trip fuel consumption and estimate total travel costs easily.

Before a road trip, one question comes up quickly: how much will the fuel cost? The answer depends on three things you can find out in advance: how far you are going, how much fuel your vehicle uses per 100 km, and what a litre of fuel costs where you buy it. This free calculator turns those numbers into the litres you need and the estimated cost of the trip.

It handles one-way and return trips and can compare two vehicles side by side, including vehicles that use different fuels. It does not include or assume any fuel price: you type the price you actually pay, so the result never relies on an outdated figure.

Fuel Cost Calculator

The fuel cost calculator is loading. If this message does not disappear, JavaScript did not start on this page. See the troubleshooting note below the tool.

Troubleshooting: if you still see the "loading" message above, JavaScript did not start. Reload the page, make sure JavaScript is enabled, and try another browser. If the tool says that BigInt is not supported, the calculator has turned itself off, and you should update your browser.

How to use the fuel cost calculator

1. Enter the distance. Type the one-way distance in kilometres, then choose One way or Return trip. The return option counts the same distance back, so it doubles the distance.
2. Enter the fuel price. Type the price per litre that you pay. Check the pump, a receipt or your usual station. The tool never fills this in for you. The currency menu only changes the symbol in the result.
3. Enter the consumption. Use litres per 100 km. If you know kilometres per litre instead, divide 100 by that number first.
4. Compare if you want. Tick Compare with a second vehicle, enter its consumption, and keep the shared price or untick the box to enter a separate price for vehicle B.
5. Press Calculate. You get the fuel needed, the estimated cost and the cost per km for each vehicle. With two vehicles you also get the difference in litres and in cost. Use Copy result to save it, or Reset to start again.

Worked examples

The prices in these examples are made up to show the arithmetic. They are not current fuel prices. Replace them with the price you pay.

Example 1: a one-way and a return trip

Inputs: 120 km one way, 7.5 L/100 km, 1.40 per litre.
One way: 120 × 7.5 ÷ 100 = 9.00 litres, and 9 × 1.40 = 12.60.
Return trip: the distance becomes 240 km, so the fuel is 18.00 litres and the cost is 25.20. The cost per km is 0.105.

Example 2: a longer trip

Inputs: 350 km one way, 9.2 L/100 km, 1.65 per litre.
Result, one way: 32.20 litres and a cost of 53.13. For a return trip, the figures double: 64.40 litres and 106.26.

Example 3: comparing two vehicles with the same fuel

Inputs: 320 km one way, 1.60 per litre. Vehicle A uses 7.5 L/100 km, and vehicle B uses 5.2 L/100 km.
Result: vehicle A needs 24.00 litres and costs 38.40. Vehicle B needs 16.64 litres and costs 26.62 (the exact value is 26.624, rounded to two decimals). Vehicle B needs 7.36 litres less, and costs 11.78 less, which is 30.7% less than vehicle A.

Example 4: two vehicles that use different fuels

Inputs: 150 km each way, return trip (300 km). Vehicle A: 7.0 L/100 km at 1.50 per litre. Vehicle B: 5.8 L/100 km at 1.55 per litre.
Result: A needs 21.00 litres and costs 31.50. B needs 17.40 litres and costs 26.97. B saves 4.53, which is 14.4% less.

Example 5: fewer litres is not always cheaper

Inputs: 100 km one way. Vehicle A: 6.0 L/100 km at 1.20 per litre. Vehicle B: 5.0 L/100 km at 1.50 per litre.
Result: B needs 1.00 litre less (5.00 against 6.00), but it costs 7.50 against 7.20 for A, because its fuel is more expensive. That is why the tool lets you enter a separate price for each vehicle.

The formulas

• Distance counted = one-way distance (× 2 for a return trip)
• Fuel needed (litres) = distance counted × consumption ÷ 100
• Estimated cost = litres × price per litre
• Cost per km = consumption ÷ 100 × price per litre
• Converting km per litre to L/100 km = 100 ÷ km per litre
• Percentage saved = (higher cost − lower cost) ÷ higher cost × 100

The calculator uses exact arithmetic with whole numbers and fractions, and rounds only for display: litres and money to two decimals, cost per km to three decimals, and percentages to one decimal. Values exactly halfway are rounded up. If you add the rounded numbers by hand, you may see a difference of one cent, because the tool rounds the exact values.

Why real fuel use is different from the estimate

The result is only as good as the consumption figure you enter. Real consumption changes from one trip to the next. The main factors are:

• Traffic. Stop-and-go driving and long idling use more fuel per kilometre than steady driving.
• Driving style. The US government's fuel economy site says aggressive driving (speeding, rapid acceleration and hard braking) can lower mileage by roughly 15% to 30% at highway speeds and 10% to 40% in stop-and-go traffic. Its page on factors that affect fuel economy also lists idling, cold weather, short trips and a poorly tuned engine.
• Vehicle condition. Servicing, tyre pressure and engine condition all change consumption.
• Road conditions. Hills, rough surfaces, wind and weather change how hard the engine works.
• Load and equipment. Passengers, luggage, roof racks and air conditioning add to consumption.

The best figure to use is your own. Fill the tank, drive normally, fill it again, and divide the litres added by the kilometres driven, then multiply by 100. This is a general method, not an official rule. A figure from the manufacturer's brochure or the trip computer is usually a good starting point but may differ from your everyday use.

Limitations and common mistakes

• Entering km per litre instead of L/100 km. The two are opposites: a better vehicle has a lower L/100 km figure and a higher km per litre figure. The tool rejects values above 100 L/100 km and asks you to check.
• Using an old fuel price. Prices change over time and between stations and regions. Enter the price you are paying now.
• Forgetting the return leg. A one-way estimate covers only half of a round trip.
• Assuming the same fuel. Petrol and diesel cost different amounts. Use the separate price box for vehicle B.
• Costs that are not included. Tolls, parking, tyres, servicing and the time of the journey are outside this calculator.
• The return trip means the same distance back. If the way back is different, calculate the two legs separately.
• The currency selector is a label. It does not convert between currencies.
• Size limits. Up to 100,000 km, 100 L/100 km and 12 digits before the decimal point.

When this calculator is useful

• Budgeting a family trip or a business journey.
• Comparing the running cost of two cars you are thinking of buying or renting.
• Comparing a petrol and a diesel vehicle on the same route.
• Splitting a trip cost with passengers. Calculate the total, then divide it by the number of people yourself.
• Checking how a change in the fuel price affects your trip. Use our Percentage and Discount Calculator to work out the percentage change between two prices.

Frequently asked questions

How is the fuel needed calculated?

The calculator multiplies the distance counted by the consumption in litres per 100 km, then divides by 100. For 200 km at 8 L/100 km, that is 200 × 8 ÷ 100 = 16 litres.

Does the calculator include fuel prices?

No. You enter the price per litre yourself. Fuel prices change over time and differ between stations and regions, so the tool never shows or assumes a price.

How do I find my vehicle's consumption?

Check the manual or the trip computer, or measure it yourself by filling the tank, driving normally and refilling: litres added ÷ kilometres driven × 100. If you only know kilometres per litre, divide 100 by that number.

Why is my real fuel use different from the estimate?

Traffic, driving style, vehicle condition and road conditions all change consumption, and so do load, weather and speed. The tool uses one average figure, so treat the result as an estimate.

Can I compare two vehicles that use different fuels?

Yes. Tick the comparison box, untick "Use the same fuel price for both vehicles", and enter a price for vehicle B. The result shows the difference in litres and in cost.

Does the tool store or send what I enter?

No. The calculation runs in your browser and the tool does not send, save or log your numbers. As with any page on this site, the page itself may load ads or analytics described in our Privacy Policy.

Conclusion

Enter your own distance, your own consumption and the price you actually pay, and treat the result as a planning estimate rather than a guarantee. For more free tools, try our Percentage and Discount Calculator or the Digital Unit Converter.