Fuel Cost Calculator
Estimate the fuel cost of any trip from distance, fuel efficiency, and fuel price.
Reviewed by the ToolNestr Editorial Team — July 2026
How fuel cost is calculated
The calculator converts all inputs to a common internal base — kilometres for distance, L/100km for fuel efficiency, and dollars per litre for fuel price. From there the math is simple:
Worked example
You drive 300 km in a car that averages 7 L/100km. Fuel costs $1.80/litre. You share the trip with 3 people.
Unit conversions explained
The calculator handles four efficiency units and two distance units seamlessly. Here is how each conversion works under the hood.
| Input unit | Conversion to base | Example |
|---|---|---|
| L/100km | Already base | 7 L/100km |
| km/L | 100 ÷ km/L | 14.3 km/L = 7 L/100km |
| mpg | 235.215 ÷ mpg | 33.6 mpg = 7 L/100km |
| miles → km | miles × 1.609 | 186 miles = 300 km |
| $/gal → $/L | $/gal ÷ 3.785 | $6.80/gal = $1.80/L |
When you select mpg, the fuel price switches to dollars per gallon and is automatically converted to dollars per litre internally. When you select miles, the distance is converted to kilometres. The result for fuel needed changes accordingly — litres for metric units, gallons for imperial.
Road Trip Budgeting
Plan the fuel budget for your next road trip. Enter the total distance, your car's efficiency, and the local fuel price to know how much to set aside before you hit the road.
Splitting with Carpoolers
When you drive colleagues or friends, use the split feature to divide the fuel cost fairly. Everyone pays exactly their share based on the total trip cost.
Compare vs Other Transport
Compare the fuel cost of driving against train, bus, or plane tickets. Factor in additional passengers to see when driving becomes the more economical choice for your group.
Vehicle Comparison
Compare two vehicles side by side. See how much you would save annually by switching to a more efficient car based on your typical monthly mileage and local fuel prices.
When to use the fuel cost calculator
The fuel cost calculator is useful in a wide range of real-world situations. For long road trips, you can estimate the total fuel cost before you leave, helping you budget for the journey and decide whether to split costs with travel companions. Simply enter the total distance, your vehicle's average fuel consumption, and the current price per litre at the pump — the calculator handles the rest, including converting between kilometres and miles, and between L/100km, km/L, and mpg.
For daily commuting, the calculator helps you understand your weekly or monthly fuel spend. Multiply your one-way distance by the number of trips per week, enter your car's efficiency, and you will see exactly what percentage of your income goes to fuel. This can be eye-opening when comparing a longer but cheaper suburban commute against a shorter urban one with stop-start traffic that reduces fuel efficiency.
Carpooling is another common use case. When you drive colleagues or friends, the split feature lets everyone contribute their fair share. Instead of guessing or rounding, the calculator gives a precise per-person cost based on the total fuel consumed. This eliminates awkwardness and ensures the driver is not left subsidising everyone else's travel.
The calculator is also valuable when comparing driving to other modes of transport. If a train ticket costs $45 and the fuel for a 300 km round trip in your car at 7 L/100km and $1.80/L is $37.80, driving is cheaper — especially with two or more people sharing the cost. For longer trips, include accommodation and tolls for a more complete comparison.
Tips for accurate estimates
Real-world fuel efficiency is worse than brochure
Manufacturers test under ideal conditions. Real-world driving typically returns 10–15% lower efficiency than the official figure. Add a margin of 10% to the consumption value for a more realistic estimate — use 7.7 L/100km instead of 7 L/100km, for example.
City vs highway makes a big difference
Stop-start city driving can increase fuel consumption by 20–40% compared to steady highway cruising. Many cars display separate city and highway figures. Use the one that matches your route, or average the two if the trip is mixed.
Fuel price varies by location
Check the current price at the pump rather than relying on a national average. Prices can vary significantly between stations on the same street, and even more between states or countries. Apps like GasBuddy or PetrolPrices show real-time local rates.
Vehicle load and driving style matter
A fully loaded car with roof rack or trailer consumes 10–20% more fuel. Aggressive acceleration and braking also increase consumption significantly. Smooth driving and removing unnecessary roof loads can improve efficiency noticeably.
How to use the fuel cost calculator
Enter trip details
Type the trip distance, choose km or miles, enter your car's fuel efficiency, and select the unit that matches your car's dashboard.
Add price and split
Enter the fuel price (per litre or per gallon) and optionally set how many people to split the cost between. Defaults to 1 for solo travel.
Calculate and budget
Click Calculate to see fuel needed, total cost, and cost per person. Adjust inputs to compare different scenarios instantly.
Fuel efficiency by vehicle type
Different types of vehicles have vastly different fuel consumption, and knowing where your car sits on the spectrum helps set realistic expectations. Small hatchbacks and hybrids typically achieve 4–6 L/100km (47–59 mpg), making them the most economical choice for commuting and city driving. Mid-size sedans and family SUVs range from 7–10 L/100km (24–34 mpg), while large SUVs, pickup trucks, and performance cars can consume 12–18 L/100km (13–20 mpg). At the extreme end, a heavy-duty truck towing a trailer might use 25+ L/100km (less than 10 mpg).
When you enter your vehicle's efficiency into the calculator, you can instantly see the fuel cost for any trip. If you are shopping for a new car, run the numbers with your typical monthly mileage and local fuel price to estimate annual fuel savings between models. A car that uses 6 L/100km instead of 9 L/100km saves 33% on fuel — over 20,000 km per year at $1.80/L, that is $1,080 saved annually.
For electric vehicle owners, see the EV Charging Cost Calculator and the EV Trip Planner for equivalents. The EV Charging Time Calculator helps estimate how long a top-up takes.
Fuel consumption vs CO₂ emissions
Fuel consumption is directly linked to CO₂ emissions. Burning one litre of petrol produces about 2.31 kg of CO₂, while diesel produces about 2.68 kg per litre. Multiply the litres used by the appropriate factor to estimate your trip's carbon footprint. For the 300 km example above — 21 litres of petrol — the trip produces about 48.5 kg of CO₂. For a deeper analysis, check the EV CO₂ Savings Calculator to compare petrol and electric vehicle emissions.
Related tools
Frequently asked questions
Where do I find my car fuel efficiency?
The manual or onboard computer; or track litres used over a known distance.
Does it work in mpg?
Yes — switch the efficiency unit and it converts internally.
Does it include tolls or parking?
No — fuel only; add those separately.
How accurate is the estimate?
Real-world efficiency is usually ~10% worse than the brochure figure — pad it for accuracy.
Sources & references
This tool uses standard formulas and reference values from:
- • SAE International standards (e.g. J1349 engine power, J1634 EV range). sae.org
- • U.S. DOE / EPA — fueleconomy.gov, official efficiency, MPGe and charging figures. fueleconomy.gov
- • Vehicle manufacturer service specifications — always defer to the OEM figures for your specific vehicle.
General estimates. Follow your manufacturer’s published specifications and a qualified mechanic for safety-critical work.