Road Trip Cost Calculator

Trip fuel cost depends on three inputs: how far you are going, how efficient your car is, and what the fuel costs. For a petrol car, the formula is distance / MPG x fuel price per litre / 4.546 (the litres-to-gallons conversion). A 500-mile trip in a car doing 45 MPG at £1.45/litre costs about £73. The calculator handles the conversion automatically, accepts both miles and kilometres, and lets you split costs across passengers for a true per-head figure on group trips.

For electric cars, the maths flips: distance x kWh per mile x electricity price. A Tesla Model 3 at 0.23 kWh/mile doing 500 miles uses 115 kWh; on home charging at 28p/kWh that is £32, on rapid charging at 75p/kWh it is £86. The calculator switches between the two modes based on fuel type, which makes EV trip planning a lot more honest than just trusting the dashboard's predicted range.

Manufacturer MPG figures (now WLTP, previously NEDC) are measured under controlled laboratory conditions and are roughly 20 to 30% better than real-world fuel economy. A car listed at 55 MPG combined typically returns 40 to 45 MPG in mixed UK driving. Motorway-only driving at 70 to 80 mph is worse still: the same car often returns 35 MPG at sustained motorway speeds because aerodynamic drag scales with the square of speed.

Use the figure from your car's actual trip computer for the most realistic estimate; reset it on a long drive and read the average after. Failing that, real-world databases like Spritmonitor or What Car? aggregate user-reported MPG and tend to be 5 to 10% below the manufacturer number, which is a good middle ground. Underestimating MPG (assuming 35 when reality is 45) inflates the trip cost by 30%; the calculator is only as accurate as the efficiency input.

On a group trip, the per-passenger cost is the trip cost divided by the number of people in the car. The calculator handles this directly: enter passengers, see cost per head. This is the number to send around the WhatsApp group when sorting out who owes the driver. £73 of fuel split four ways is £18.25 per person, which is roughly the cost of a London-to-Manchester train ticket if you booked weeks ahead.

Bear in mind some passengers may eat more service-station cost than others (driver stays focused, three passengers eat £45 worth of M6 services food). Fuel-only splitting is the cleanest method; food and tolls are typically not in the per-head calculation unless explicitly added. For a multi-day trip, the [petrol vs electric total cost calculator](/petrol-vs-electric-total-cost) gives a more complete picture by including hotel and per-day vehicle wear.

On a single-driver trip of 200+ miles, the train often loses on price (£100+ off-peak vs £30 of fuel) but wins on time and comfort. With 2 passengers, the car wins on price (£15 each vs £100 each by rail) and matches on time door-to-door if the destination is not a city centre. With 4 passengers, driving is dramatically cheaper and the comfort gap closes if you have a comfortable car.

Add tolls, parking and congestion charges to the picture for city destinations. The Dartford Crossing is £2.50 each way; central London is the £15 ULEZ daily charge plus the £15 congestion charge plus £30+ for parking. Suddenly a £30 trip becomes £80. The calculator shows the fuel cost only; add a mental £20 to £50 for any city-centre drive to get a realistic total.