How to Calculate Trip Fuel Cost

Use total distance and real-world economy

Include the return leg, detours and local driving. Real-world economy is often more useful than a laboratory or best-case figure.

For US units, miles divided by miles per gallon gives gallons. For metric km/L, kilometers divided by km/L gives liters.

Do not mix economy formats

Liters per 100 km is a consumption rate, so its formula differs: liters = distance × L/100 km ÷ 100.

Convert the vehicle's figure or select a calculator mode that matches it before estimating.

• km/L: distance ÷ efficiency
• mpg: distance ÷ efficiency
• L/100 km: distance × consumption ÷ 100

Build a complete trip budget

Fuel is only one driving cost. Tolls, parking, ferries and congestion charges can materially change the comparison with rail or air travel.

Splitting the total by passengers is useful for budgeting, but it does not change the vehicle's operating cost.