MPG and L/100km point in opposite directions
Miles per gallon measures how far the fuel takes you — bigger is better. Liters per 100 km measures how much fuel the distance costs you — smaller is better. The conversion is 235.2 ÷ value in either direction: 30 MPG is 7.8 L/100km. The calculator handles whichever system you pick, so no conversion is needed.
Your real-world consumption is not the brochure number
Official figures come from laboratory cycles; real driving with hills, climate control and a loaded car typically runs 10–20% thirstier. For an honest number, fill the tank, drive normally until the next fill, and divide fuel added by distance covered. Use that figure here and the cost estimate becomes reliable enough to settle who owes what.
Splitting fairly
The per-person figure divides fuel only. If the trip also involves tolls or wear, common practice is fuel × 1.5 as a fair contribution per car, then divided by everyone including the driver — but that is etiquette, not arithmetic. The round-trip line doubles distance at the same consumption; add a margin if the return leg is loaded or hilly.
Frequently asked questions
How do I convert MPG to L/100km?
Divide 235.2 by the number, in either direction: 40 MPG = 5.9 L/100km, and 8 L/100km = 29.4 MPG. Note that UK MPG uses a larger gallon — multiply US MPG by 1.2 to compare.
Why is my winter consumption higher?
Cold engines run rich for the first kilometres, winter fuel blends carry slightly less energy, and heating plus denser air add load. A 10–15% winter penalty is normal — measure a winter tank separately if you drive short trips in the cold.
Is my data stored or sent anywhere?
No. Your route and prices are not sent anywhere.
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