Fuel Cost Calculator: What a Journey Costs to Drive
Fuel cost is distance divided by fuel economy, multiplied by the price per litre or gallon. Enter the trip distance, your vehicle's consumption and the current pump price to get the cost of a single journey, a daily commute or an annual mileage total.
Getting the maths right in each unit system
In imperial terms, cost = miles ÷ mpg × price per gallon. In metric, cost = km ÷ 100 × litres per 100 km × price per litre. Do not mix the two: US and imperial gallons differ by about 20%, so a UK mpg figure applied to US gallons will understate your fuel use significantly.
Real economy is worse than the sticker
- Official figures are lab-tested; real-world use is typically 10-20% higher.
- Speeds above about 60 mph / 100 km/h increase consumption sharply from aerodynamic drag.
- Roof boxes and bike racks can add 10-25% on motorway journeys.
- Under-inflated tyres, short cold trips and heavy loads all cut economy.
Comparing with an EV or public transport
For an electric vehicle, use kWh per 100 miles or per 100 km with your electricity price. Home charging usually costs a fraction of petrol per mile, while rapid public charging narrows the gap considerably. When comparing against rail or coach, include parking and tolls in the driving figure — they often exceed the fuel itself on city trips.
Key takeaways — Fuel Cost Calculator
- Cost = distance ÷ fuel economy × fuel price, in consistent units.
- Track real consumption from fill-ups rather than trusting official figures.
- Include tolls, parking and depreciation for a true cost per journey.