How is fuel cost calculated?

For metric: fuel used = distance ÷ 100 × L/100km consumption. Total cost = fuel used × price per litre. For imperial: fuel used = distance ÷ MPG. Total cost = fuel used × price per gallon.

Does this account for motorway vs city driving?

The calculator uses a single fuel economy figure you provide. For mixed trips, use an average between your city and motorway consumption, or use your car's combined figure from the manufacturer spec sheet.

Can I calculate cost for multiple passengers?

Yes — enter the number of people and the calculator shows both the total fuel cost and the cost per person split evenly.

Road Trip Cost Calculator — Fuel Cost & Per-Person Split

Distance (km)

Fuel economy (L/100km)

L/100km

Fuel price (per litre)

€/ L

Average speed

km/h

Number of people

people

Extra stops / detours

Trip summary

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Total fuel cost

—

Per person

—

Total distance

—

Fuel used

—

Drive time

—

Cost per km

About the Road Trip Calculator

A road trip cost calculator helps budget accurately for long journeys by combining distance, vehicle fuel economy, and current fuel price. The tool also splits the total cost among passengers — useful for group travel where expenses should be divided fairly. Accurate budgeting requires real-world fuel consumption rather than official WLTP figures, which are typically 15-20% optimistic.

Factors affecting real-world fuel consumption

Speed — fuel use rises significantly above 60 mph due to aerodynamic drag. At 80 mph you typically use 20% more than at 60 mph.
Load — a fully laden car uses more fuel. Roof boxes and bike racks add significant drag.
Terrain — hilly routes increase consumption; motorway driving is more efficient than stop-start urban driving.
Air conditioning — increases fuel use by 5-10% in city conditions.

UK MPG vs metric L/100km

To convert UK MPG to litres per 100km: L/100km = 282.48 ÷ MPG. Example: 40 MPG = 7.06 L/100km. Note that UK and US gallons differ (UK = 4.546L, US = 3.785L), so UK and US MPG figures for the same car will give different numbers.

Planning fuel stops on long journeys

On long motorway drives, planning fuel stops in advance avoids paying motorway service station prices (typically 10-20p/litre more than local stations) and prevents low-fuel anxiety on unfamiliar routes. Fill up at supermarket forecourts near motorway junctions rather than at service stations. Apps like Waze and PetrolPrices.com show live prices on your route.

Fill up before motorways — prices at service stations are significantly higher than nearby town stations
Fuel range planning — know your car's approximate range and plan stops before the quarter-tank mark
Supermarket forecourts — Asda, Tesco, and Sainsbury's near motorway junctions offer competitive prices
Loyalty points — filling up at supermarket forecourts earns loyalty points that add up over long trips

Frequently Asked Questions

How do I calculate fuel cost for a road trip?

Formula: Cost = (Distance ÷ MPG) × litres-per-gallon × fuel-price. For miles and UK MPG: litres needed = (miles / MPG) x 4.546. Cost = litres x price per litre. Example: 300 miles at 40 MPG = 7.5 gallons = 34.1 litres. At 1.55 per litre = 52.86 total.

How should road trip costs be split between passengers?

The simplest method is dividing total fuel cost equally by the number of people in the car, including the driver. Enter the number of passengers in the calculator to see the per-person share automatically.

How does motorway speed affect fuel economy?

Aerodynamic drag increases with the square of speed, making higher speeds disproportionately expensive. Driving at 70 mph uses around 10% more fuel than 60 mph; driving at 80 mph uses 20-25% more. For maximum efficiency on long motorway trips, maintain 60-65 mph in a higher gear.

What is the difference between UK and US MPG?

The UK gallon (4.546 litres) is larger than the US gallon (3.785 litres). The same car driven identically gives a higher MPG number in UK measure than US measure. 40 MPG UK equals approximately 33 MPG US. Always check which standard applies when comparing specifications.

How do I calculate fuel cost per mile?

Multiply your fuel consumption in litres per mile by the fuel price. Litres per mile = 4.546 / MPG (UK). At 1.55 per litre and 40 MPG UK: 4.546/40 = 0.1137 L/mile. Cost = 0.1137 x 1.55 = 17.6 pence per mile.