Split fuel and toll costs

The calculation covers three items: fuel, tolls and parking. Fuel is easy to work out from the distance, the car's average consumption and the price per litre of the fill-up you actually paid for.

Wear and tear, insurance and servicing are not necessarily passed on between friends. If you do want to include them, one clear method is a per-kilometre allowance announced before departure, added here as an extra cost.

One possible practice among friends is that the driver pays a share like everyone else, since they are travelling too. They may front the costs, which is precisely why it helps to compute what each passenger owes them.

Some groups exempt the driver from part of the costs to offset fatigue and wear on the car. That is perfectly fine, as long as it is agreed before leaving: enter fewer legs for them, or deduct a fixed amount from the total.

Counting legs rather than people handles most real situations: a passenger picked up halfway, someone taking the train home, a carpool where the group changes between the outbound and return trip. Each leg travelled counts as one unit and the split follows.