MPG Calculator
Calculate your vehicle's fuel economy from miles driven and fuel used, or estimate how much fuel and money a planned journey will cost. Uses UK imperial gallons (1 gallon = 4.54609 litres).
Calculate MPG from a journey
Enter miles driven and fuel used to find your MPG, L/100km, and cost per mile.
Related: Fuel Efficiency · Fuel Cost · Trip Cost
Plan a journey
Enter your MPG and journey distance to estimate fuel needed and cost.
How the MPG Calculator works
The MPG Calculator has two modes. The first calculates your car's real-world fuel economy: enter the miles driven and the fuel consumed (in litres or UK gallons) and the calculator returns MPG, L/100km, km/L, and — if you enter a pump price — the total fuel cost and cost per mile. This is the most accurate way to measure your vehicle's actual consumption rather than relying on manufacturer claims.
The second mode is a journey planner: enter your known MPG and a planned distance to find out how many litres of fuel you will need and what it will cost at a given pump price. This helps with long-distance trip planning, particularly for electric-range anxiety checks or when comparing the economics of different vehicles before a purchase.
All calculations use the UK imperial gallon (4.54609 litres), which is larger than the US gallon. This distinction matters when comparing UK-spec fuel economy data with US sources: a car claiming 30 MPG on the US cycle is not as efficient as one claiming 30 MPG on the UK cycle, because the UK gallon holds more fuel.
Frequently asked questions
What does MPG mean?
MPG stands for miles per gallon and measures how far a vehicle travels on one gallon of fuel. In the UK, this uses the imperial gallon, which equals 4.54609 litres — larger than the US gallon (3.785 litres). A higher MPG means better fuel economy and lower running costs. UK car manufacturers quote MPG figures based on official WLTP testing.
What is a good MPG for a UK car?
For a petrol car in the UK, 40–50 MPG is considered reasonable, while 55 MPG or above is good. Diesel cars typically achieve 50–65 MPG due to the higher energy density of diesel. Hybrid vehicles can return 60–80 MPG in mixed driving. Any figure below 30 MPG — common in older, larger, or high-performance cars — represents relatively poor economy and higher fuel spend.
How do I calculate my car's MPG?
To calculate your real-world MPG, fill your tank completely and note the mileage. Drive normally until you need to refuel, then fill up again and note the number of litres added. Convert litres to UK gallons by dividing by 4.54609. Divide the miles driven by the gallons used. For example: 300 miles on 30 litres = 300 ÷ (30 ÷ 4.54609) = approximately 45.5 MPG.
How does MPG compare to litres per 100km?
L/100km is the standard measure used in most of Europe: it shows how many litres are consumed per 100 kilometres. A lower L/100km means better efficiency — the opposite of MPG. To convert UK MPG to L/100km, divide 282.5 by the MPG figure. For example, 45 MPG ≈ 6.3 L/100km. To convert L/100km back to UK MPG, divide 282.5 by the L/100km value.