Fuel Cost Calculator
Estimate the fuel cost of any trip in metric or imperial units, then project that to weekly and annual spend. Toggle round-trip, compare a second vehicle, or split city and highway driving to see how your real-world mix changes the bill.
Formula
Worked example
Metric: 100 km at 8 L/100km and 1.80/L: 8 L x 1.80 = 14.40. Imperial: 62 miles at 30 MPG and 3.80/gal: 62/30 = 2.07 gal x 3.80 = 7.87. At 5 trips/week, 14.40 x 5 x 52 = 3,744 per year.
How the fuel cost calculation works
The calculator converts every fuel-economy figure to litres per 100 km internally, so the math is the same regardless of whether you enter L/100km, km/L, or US MPG. Fuel used equals distance in km divided by 100, multiplied by the L/100km rate. That volume is then multiplied by the price per litre (metric) or converted to US gallons and multiplied by the price per gallon (imperial). Round-trip simply doubles the one-way distance. Annual projection multiplies the per-trip cost by your weekly trips and then by 52.
City vs highway driving and why the mix matters
Stop-and-go city driving uses significantly more fuel per kilometre than steady highway cruising because the engine idles at traffic lights and acceleration from standstill is energy-intensive. Official fuel-economy ratings in the US and EU are tested separately for city and highway cycles. Enable the city/highway split option to enter both figures and your estimated highway percentage: the calculator weights them into a single blended consumption rate. A typical commuter might be 40% highway and 60% city, while a long interstate drive is 90% or more highway.
Comparing two vehicles and projecting annual savings
The second-vehicle comparison lets you enter the fuel economy of an alternative car and see how much you would save (or spend extra) over a full year. Because annual savings compound the small per-trip difference across hundreds of trips, even a modest improvement from 9 L/100km to 7 L/100km translates into hundreds of dollars per year for a daily commuter. The annual saving output assumes both vehicles make the same number of trips at the same fuel price, isolating fuel economy as the only variable.
Limitations to keep in mind
Fuel economy figures vary with speed, load, climate, and driving style. The official rating from a manufacturer may understate real-world consumption by 10-20% under laboratory conditions. This calculator does not include tolls, parking, depreciation, oil, tyres, or insurance, all of which are part of the true cost of a trip. Use the result as a planning estimate and check current pump prices before a long drive.
Typical fuel economy by vehicle type
| Vehicle type | L/100km | km/L | US MPG |
|---|---|---|---|
| Compact hybrid (e.g. Toyota Yaris Hybrid) | 3.5-5.0 | 20-29 | 47-67 |
| Small petrol hatchback | 5.5-7.5 | 13-18 | 31-43 |
| Mid-size sedan (petrol) | 7.0-9.0 | 11-14 | 26-34 |
| Large SUV / pickup (petrol) | 10-14 | 7-10 | 17-24 |
| Full-size diesel truck | 8-12 | 8-12 | 20-29 |
| Plug-in hybrid (petrol mode) | 4.5-6.5 | 15-22 | 36-52 |
Real-world mixed-driving figures; official lab ratings are often 10-20% better.
Frequently asked questions
What is a typical fuel consumption rate for a passenger car?
Most modern petrol passenger cars consume between 6 and 10 litres per 100 km under mixed driving conditions. Smaller hatchbacks and hybrids can reach 4-5 L/100km, while large SUVs and pickups often exceed 12 L/100km. In MPG terms, efficient small cars reach 40-50 MPG US while full-size trucks typically return 15-22 MPG.
How do I convert between L/100km, km/L, and MPG?
To convert US MPG to L/100km, divide 235.21 by the MPG figure. To convert L/100km to km/L, divide 100 by the L/100km value. For example, 30 US MPG is approximately 7.84 L/100km and 12.74 km/L. UK imperial gallons are about 20% larger than US gallons, so UK MPG to L/100km uses 282.5 instead of 235.21.
Does driving at higher speeds significantly increase fuel cost?
Yes. Aerodynamic drag grows with the square of speed, so driving at 110 km/h (68 mph) typically burns 10-15% more fuel per kilometre than driving at 90 km/h (56 mph). The US Department of Energy estimates that each 8 km/h above 80 km/h reduces fuel economy by roughly 7-14%. Maintaining a moderate, consistent speed is one of the most effective ways to reduce fuel costs on long trips.
How does the round-trip option work?
Toggling round trip doubles the distance before computing fuel used and cost, on the assumption that the return journey covers the same road and driving conditions. If your outbound and return routes differ in distance or terrain, calculate each leg separately and add the results.
What is the annual projection based on?
The annual fuel spend is calculated as: one-way trip cost multiplied by trips per week multiplied by 52 weeks. If you make 5 one-way trips of 20 km each weekday, enter 5 trips per week and 20 km as the distance. Adjust trips per week for part-time schedules, school terms, or seasonal variation.