You pick up a hire car abroad, pull into a station, and the pump is priced per litre while the dash counts kilometres and the brochure quoted economy in figures that mean nothing to you. A little familiarity — or a quick converter — turns that from a headache into a non-issue.
The units you'll actually meet
Most of the world sells fuel by the litre and measures distance in kilometres. Some countries, notably the US, use gallons and miles — and a US gallon and an imperial gallon aren't the same size, the imperial gallon being larger. That difference alone can throw off your sense of a price or a car's economy if you assume they're identical. Fuel economy itself is expressed two opposite ways: "miles per gallon" or "kilometres per litre," where higher is better, versus "litres per 100 km," where lower is better. Same thing, opposite directions — which is why a figure can look alarming until you know the system.
Why it matters for your budget
Getting the units straight isn't pedantry — it directly affects what you'll spend. A price that looks cheap per litre can add up fast over a long road trip, and a price that looks high per gallon may actually be reasonable once converted. To estimate a trip's fuel cost you need three things in compatible units: the distance, the car's consumption, and the fuel price. Mix metric and imperial without converting and your estimate can be wildly off.
Convert it here
Estimate yours below — keep all three numbers in the same language so your fuel budget reflects reality, not a units mix-up.
Convert → fuel & distance units
Indicative only — confirm the correct fuel type and current local prices for your specific trip.
A few habits for driving abroad
Note which fuel type your hire car takes — petrol versus diesel, and the correct grade — because filling with the wrong one is an expensive mistake. Learn the local words for fuel types so you don't guess at the pump. Understand whether stations are self-service or attended, and how payment works, since some require prepayment or a local card. And check your rental's fuel policy: "full to full" usually works out cheapest if you return it filled, while prepaid-fuel deals often cost more than they seem.
Go deeper
Questions
Is a US gallon the same as an imperial gallon?
No — the imperial gallon is larger than the US gallon. Assuming they're the same will distort any price or fuel-economy comparison, so always check which gallon a figure refers to before converting or comparing.
What's the difference between mpg and litres per 100km?
They measure the same thing from opposite directions. With miles per gallon (or km per litre), higher is more efficient. With litres per 100 km, lower is more efficient. Knowing which system you're looking at prevents misreading a car's economy.
How do I estimate fuel cost for a road trip?
You need the distance, the car's fuel consumption and the fuel price — all in compatible units. Convert everything to one system first, then estimate. Mixing metric and imperial without converting is the main way these estimates go badly wrong.
Does fuel type matter in a hire car?
Very much — putting the wrong fuel in (petrol in a diesel car or vice versa) is a costly mistake. Check what your rental takes and the correct grade, and learn the local words for fuel types so you don't guess at the pump.
Which rental fuel policy is cheapest?
Usually "full to full" — you collect the car full and return it full, paying only for what you use. Prepaid-fuel deals often cost more than they appear, since you rarely return the tank empty and don't get a refund for what's left.
How do I judge if fuel is expensive there?
Convert the local price into a unit and currency you understand before judging it. A per-litre price and a per-gallon price feel very different but may be similar once converted, so translate first rather than reacting to the raw number on the sign.
Fuel prices, units and rental policies vary by country and change over time. This is general guidance only — always confirm the correct fuel type and current local prices for your specific trip.