About this calculator
The Fuel Cost Calculator estimates the petrol or diesel cost of a journey from distance, MPG, and fuel price per litre. It helps drivers budget for commuting, delivery work, holidays, school runs, business mileage, and long-distance trips. Because UK fuel is sold by the litre while many cars are described in MPG, the calculator converts UK MPG into litres used before multiplying by the pump price.
Fuel Cost Calculator method
This calculator uses straightforward fuel economy, vehicle measurement, or unit conversion formulas. Results are estimates for planning and comparison, so real-world driving, vehicle condition, load, weather, route type, and manufacturer data can change the outcome.
- litres used = miles / MPG x 4.54609
- fuel cost = litres used x price per litre
- cost per mile = fuel cost / miles
How to use the Fuel Cost Calculator
- Enter the main vehicle or journey figures requested by the calculator.
- Use UK units where shown, especially miles, litres, UK MPG, and prices per litre.
- Check whether the calculator is asking for measured real-world figures or official brochure figures.
- Review the headline result and the supporting breakdown below it.
- Compare at least two scenarios if you are choosing between vehicles, journeys, or running-cost assumptions.
- Adjust one assumption at a time to see which input changes the result most.
- Use the result as an estimate, then confirm important decisions with real quotes, vehicle records, or specialist advice.
Worked examples
Weekend trip
Input: 220 miles, 45 MPG, GBP 1.45 per litre
Calculation: 220 / 45 x 4.54609 = 22.22 litres; 22.22 x 1.45
Result: About GBP 32.22
Daily commute
Input: 30 miles per day, 40 MPG, GBP 1.50 per litre
Calculation: 30 / 40 x 4.54609 = 3.41 litres; 3.41 x 1.50
Result: About GBP 5.11 per day
Using realistic fuel prices
Fuel prices vary by area, motorway services, supermarket stations, fuel type, and time. Use the price you expect to pay, or run low and high price scenarios if you are planning future costs.
Business and shared journey use
The calculator can help estimate a journey cost before splitting fuel with passengers or recording a business trip. It is not a tax mileage allowance calculator; use official mileage rules or employer policy for reimbursement decisions.
Why real-world results vary
Fuel economy and running costs can shift noticeably from the calculated result. Short trips, cold starts, roof boxes, tyre pressure, motorway speed, stop-start traffic, heavy loads, air conditioning, and poor servicing can all increase fuel use.
For buying decisions, compare a conservative scenario as well as an optimistic one. A car that looks cheaper on official MPG may cost more if your real-world driving pattern is mainly urban or short-distance.
Common mistakes and edge cases
- Short urban journeys often cost more than a steady-route MPG estimate suggests.
- Towing, roof boxes, and heavy loads can increase fuel use.
- Motorway service station fuel may be more expensive than local pump prices.
- Do not use pence per litre as pounds unless the input specifically asks for pounds.
Limitations
This calculator is for general information only. It is not financial, engineering, insurance, valuation, or mechanical advice.
- It estimates fuel only and excludes parking, tolls, insurance, servicing, tyres, depreciation, and finance.
- It assumes one MPG figure applies across the whole journey.
- It does not replace employer, HMRC, or accounting rules for mileage claims.
Frequently asked questions
Can I use this for petrol and diesel?
Yes. Enter the correct price per litre for the fuel you use.
Does it include electric charging?
No. Use an EV charging or EV versus petrol calculator for charging costs.
Why does cost per mile matter?
It helps compare journeys, commuting costs, and the effect of different MPG assumptions.
Can I estimate a monthly commute?
Yes. Calculate one round trip, then multiply by the number of commute days.
Should I use official MPG?
Use real-world MPG if you have it. Official MPG is useful for comparison but may be optimistic.
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