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total fuel cost
Fuel economy comes in mutually confusing units: Europe counts litres per 100 km (lower is better), while the UK and US both use miles per gallon — with gallons of different sizes, so 40 mpg UK equals about 33 mpg US. This calculator accepts any of them, plus km per litre, converts internally and prices the trip in whatever currency your fuel price is in.
Official consumption figures flatter real driving by 10–20%; motorway cruising with luggage and passengers sits closer to the official 'highway' number plus a margin. If your car shows average consumption on the trip computer, use that. The per-person split makes cost-sharing trivial — and comparing it against train or flight prices often changes the plan.