The Fuel Cost Calculator prices a journey's fuel before you take it: enter the distance, your vehicle's fuel economy, and the fuel price, and it returns the fuel required, the total cost, the cost per mile (or per kilometre), and a monthly cost projection from your typical monthly distance. Imperial (miles, MPG, price per gallon) and metric (kilometres, litres per 100 km, price per litre) modes are both supported.
How It Works
In metric mode the economy figure is consumption (litres per 100 km), so fuel needed is distance x consumption / 100, and the calculator reports the volume in both gallons and litres for cross-checking.
Parameters
| Input | Required | Meaning | |---|---|---| | Distance | Yes | Trip length, miles or kilometres | | Fuel economy | Yes | MPG (imperial) or L/100 km (metric) | | Fuel price | Yes | Per gallon or per litre, matching the mode | | Monthly distance | No | For the monthly projection (default 1,500) |
Worked examples
Imperial: a 300-mile road trip in a car averaging 25 MPG with fuel at 42.00**, which is 210 a month, the figure that belongs in a commuting budget. Metric: 450 km at 7.5 L/100 km with fuel at 60.75**, about $0.135 per kilometre (the calculator also shows the volume as about 8.92 gallons for anyone cross-referencing a US-spec vehicle). Note how the per-distance figure does the comparative work: it prices any two journeys, vehicles, or fuel prices against each other instantly, and multiplied by annual distance it is the energy line of a cost-per-mile ownership estimate.
Getting an honest economy figure
The calculation is exact; the input decides whether the answer is. Rated MPG (EPA, WLTP) is a laboratory figure that real driving undershoots by typically 10 to 20%, more in cold weather, short trips, and aggressive traffic. Your own measured figure, from fill-to-fill records or the MPG Calculator on this site, converts this tool from a brochure estimate into a budget number. Trip-specific adjustments matter at the same scale: towing or a roof box can add 20 to 30% to consumption at highway speed, mountain routes and winter conditions add their own penalties, and a heavily loaded vehicle on a summer road trip is precisely the case where travelers under-budget by using the sticker figure. When the trip matters (a relocation drive, a delivery route, a reimbursable journey), run the calculator at your measured economy and again at 15% worse, and budget the second figure.
What the number is used for
Trip budgeting is the obvious use, with three less obvious ones close behind. Expense claims and reimbursement: the cost-per-mile output documents a fuel-only claim where an employer or client reimburses fuel rather than a standard mileage rate (know which basis your policy uses; statutory mileage rates include wear and depreciation and are deliberately higher than fuel alone). Vehicle comparison: pricing the same month of driving through two candidate cars at their measured economies produces the fuel component of a purchase decision, which the EV vs Petrol Calculator extends to electric running costs. Route and behaviour decisions: a per-mile figure makes detours, idling, and the true cost of a "quick" 40-mile errand visible in currency rather than in vibes, which changes behaviour more reliably than economy gauges do.
Limitations
A steady-state estimate: it assumes the economy figure you enter holds across the whole distance, with no separate modelling of cold starts, congestion, terrain, weather, or fuel-grade differences, and the monthly projection simply scales the per-distance cost by your stated monthly distance. Fuel prices move between planning and travelling; the estimate is as current as the price you enter.
Frequently Asked Questions
Should I enter the car's rated MPG or my real MPG?
Your real, measured MPG wherever you have it: it reflects your routes, load, and climate, and it is usually noticeably worse than the rating, which is exactly why budgets built on ratings run short. The rating is acceptable for comparing vehicles you do not yet own.
Why does the metric mode ask for litres per 100 km instead of km per litre?
Because consumption per fixed distance is the standard metric presentation and the more honest comparator (it scales linearly with fuel burned). The calculator converts volumes both ways in its outputs, and the MPG Calculator on this site moves between all four conventions if you need km/L as the headline.
What does cost per mile not include?
Everything except fuel: depreciation, tyres, maintenance, insurance, tolls, and parking. A full motoring cost per mile is typically two to four times the fuel-only figure, which is why official mileage reimbursement rates look generous next to this calculator's output. They are pricing different things.