What this planner works out
This planner converts distance and economy into litres of fuel, costs it at your pump price, and divides the total between the people travelling.
The per-person figure is what makes it useful. Splitting fuel is a common arrangement and a common source of vagueness.
Enter your details
Before you split the cost
- Use observed economy rather than the brochure figure, and expect motorway driving to be worse than mixed.
- Fuel price varies substantially between motorway services and supermarkets — often 10p a litre or more.
- Decide in advance whether the driver counts as one of the people splitting. Both conventions exist and neither is wrong.
- Fuel is not the whole cost of the journey. Tolls, parking and wear are separate.
There is no standard. Some groups split fuel equally including the driver; some exclude the driver on the basis that they are providing the car and doing the driving; some split total costs including a wear allowance. What matters is agreeing which before setting off, since the difference on a long trip is enough to cause awkwardness.
How this calculator works
Distance to litres, litres to cost, cost to shares:
Litres = distance ÷ mpg × 4.54609
Total cost = litres × price per litre
Per person = total ÷ people splittingThe 4.54609 converts gallons to litres. Note the calculation covers the outward journey only — for a return trip, double the distance or the result.
Worked example: 180 miles
Using the default figures — 180 miles at 45 mpg, fuel at £1.45 a litre, split two ways:
- Fuel needed: 18.2 litres
- Total cost: £26.37
- Per person: £13.18
£13 each for a 180 mile journey, which for two people is comfortably cheaper than any train fare over that distance. Make it a return trip and it is £26.37 each. Filling at a supermarket rather than motorway services at 10p a litre less would save £1.82 on this trip — worth noting but not worth a detour, which is a calculation the Time Value Calculator handles.
Common mistakes
- Calculating one way for a return journey. Double the distance.
- Using the manufacturer's mpg. Observed economy is lower.
- Not agreeing the split beforehand. Whether the driver pays is a real question.
- Splitting fuel but ignoring tolls and parking. They can exceed the fuel on some routes.
- Assuming motorway fuel prices. They are consistently among the highest.
Frequently asked questions
Should the driver contribute to fuel?
Conventions differ. A common arrangement is that the driver contributes as an equal passenger, on the basis that they would be making the journey anyway; another is that they do not, in recognition of providing the vehicle and doing the driving. Where the trip exists only because of the passengers, the second is more usual.
Is sharing fuel costs legal?
Accepting contributions towards the running costs of a journey you are making anyway is generally fine and does not require hire and reward insurance. Charging more than the running costs, or driving specifically as a paid service, changes the position entirely and would need appropriate insurance and licensing.
Where is fuel cheapest?
Supermarkets are usually among the cheapest and motorway services consistently among the most expensive, frequently by 10 to 20p a litre. Price comparison apps and the government's fuel price transparency data make local comparison straightforward. On a long trip, filling before joining the motorway is worth doing.
Does driving style affect this much?
Considerably. Smooth acceleration, anticipating traffic, maintaining steady speeds and keeping tyres correctly inflated can improve economy by 10% or more. Roof boxes and bars are a large and often forgotten penalty — a roof box can cost 10 to 20% at motorway speeds and should come off when not in use.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — fuel price transparency data and vehicle running costs
- MoneyHelper — budgeting for travel and motoring costs
Sources are checked at publication and can change — how I choose and check references.