Know exactly what your fuel actually costs you.
Convert between US MPG, UK (imperial) MPG and L/100km, then see the real cost of any trip — built for drivers on both sides of the Atlantic.
Fuel Cost Calculator
Enter your trip details below.Why US and UK MPG aren't the same number
A US gallon is 3.785 litres. A UK (imperial) gallon is 4.546 litres — about 20% larger. That means the same car gets a higher MPG figure in the UK than in the US, even though nothing about the car has changed. Most calculators online only handle one system, which causes real confusion for drivers. Official gallon definitions are maintained by NIST (US National Institute of Standards).
Check live fuel prices before you calculate
This tool converts between all three systems and shows your actual trip cost. For live US fuel prices check GasBuddy. For UK pump prices, RAC Fuel Watch is updated weekly. Once you know your running costs, browse our fuel-efficient vehicles at Astra Automobiles to see what you could save.
Gallons, miles, dollars
Enter your US MPG rating, trip distance in miles, and price per gallon. We'll show your trip cost and convert to UK and metric units. See our vehicles →
Imperial gallons, miles, pounds
Switch to UK MPG, enter your price per litre, and get your real running cost plus US and metric equivalents. Talk to us about saving on fuel →
Thinking about a more fuel-efficient car?
Astra Automobiles can help you find one that actually lowers your running costs.