Glossary
MPG (Miles Per Gallon)
Direct Answer / TL;DR
What is MPG (Miles Per Gallon)?
A measure of fuel efficiency expressing how many miles a vehicle travels on one gallon of fuel. The higher the MPG, the more economical the car — and the less each mile costs you.
Why does it matter for UK drivers?
MPG is the UK's primary measure of fuel economy. It tells you how far your car travels on a single gallon of fuel. A small city car might achieve 50–60 MPG, while a large SUV might manage only 25–35 MPG. The difference in running costs is substantial — at 145p/litre, a car averaging 35 MPG costs roughly 18.8p per mile in fuel, while a 55 MPG car costs only 12p per mile.
To calculate fuel cost per mile, use: cost per mile (pence) = (price per litre × 4.546) ÷ MPG. The 4.546 converts from litres to UK gallons (note: US gallons are only 3.785 litres, so US MPG figures are not comparable).
MPG figures come in two main flavours in the UK: the official figure (measured on a laboratory test cycle — either NEDC or the newer WLTP) and real-world MPG, which accounts for actual driving conditions. Official figures are typically 15–25% optimistic. The UK government's VCA (Vehicle Certification Agency) publishes official figures for all new car registrations.
MPG matters enormously when calculating whether a detour to a cheaper petrol station is actually worth it. A driver in a 55 MPG hybrid will spend half as much driving to the cheap station as someone in a 28 MPG 4x4 — so the break-even distance is very different for each. WorthThePump looks up your real-world MPG estimate from your number plate to give you a personalised saving calculation rather than a generic figure.
For electric vehicles, the equivalent metric is miles per kWh (mi/kWh) or the UK's MPGe (miles per gallon equivalent). WorthThePump currently focuses on petrol and diesel — full EVs are out of scope because they don't visit fuel stations.
Related terms
Further reading
Now you know what MPG (Miles Per Gallon) means —
find out if your nearest cheap station is actually worth the trip.