Calculate Trip Fuel Cost

Petrol Cost Calculator for a UK Trip

Calculate the petrol cost of a trip the British way: distance in miles, fuel economy in MPG (imperial gallons) and the price in pence per litre. The calculator starts with the latest UK average for unleaded and diesel and can split the cost between passengers.

UK miles, MPG & pence per litre · UK fuel prices

Your trip

Sets units, currency and the average petrol price.
One way. Get it from your map app.

Your car & petrol price

Fuel type
From your dashboard, or the official figure for your car.
$

Sharing & extras optional

$
Petrol cost for the trip—
Petrol needed—
Cost per person—
Cost per mile—

Same trip with a different car

How to calculate petrol cost for a trip in the UK

UK cars quote fuel economy in miles per imperial gallon, but petrol is sold by the litre, so the sum has one extra step. One imperial gallon is 4.546 litres:

petrol cost = miles ÷ MPG × 4.546 × price per litre

For example, London to Manchester and back is roughly 400 miles. In a car doing 45 MPG that uses 40.4 litres, and at the UK average of 174.1p a litre (26 October 2026) the petrol costs about £70.35.

Petrol and diesel cost per 100 miles

At 174.1p per litre for unleaded and 199.2p for diesel:

Fuel economyLitres per 100 miPetrol per 100 miDiesel per 100 miPence per mile (petrol)
25 MPG18.2£31.66£36.2231.7p
30 MPG15.2£26.38£30.1926.4p
35 MPG13.0£22.61£25.8722.6p
40 MPG11.4£19.79£22.6419.8p
45 MPG10.1£17.59£20.1217.6p
50 MPG9.1£15.83£18.1115.8p
55 MPG8.3£14.39£16.4714.4p
60 MPG7.6£13.19£15.0913.2p

Why UK MPG figures look higher

An imperial gallon is about 20% bigger than a US gallon, so the same car returns about 20% more miles per gallon in the UK than in an American review. If you find a figure from a US site, set the economy unit to MPG (US) and the calculator converts it. European figures in litres per 100 km work too: 6 L/100 km is about 47 UK MPG.

Tips for UK drivers

  • Use your real MPG. The WLTP figure is a lab test; the trip computer shows what you really get.
  • Motorway services charge more. Filling up at a supermarket forecourt before a long run usually saves several pence a litre.
  • Diesel or petrol? Diesel costs more per litre but diesel cars usually go further on it. Switch the fuel type to compare.
  • For mileage claims, the fuel cost per mile calculator shows your pence per mile.

Frequently asked questions

How do I calculate the petrol cost of a journey in the UK?
Divide the miles by your MPG to get gallons, multiply by 4.546 to get litres, then multiply by the price per litre. 200 miles at 45 MPG = 4.44 gallons = 20.2 litres; at £1.74 a litre that is about £35.
Why are UK MPG figures different from US ones?
A UK (imperial) gallon is 4.546 litres and a US gallon is 3.785 litres, so the same car shows about 20% more MPG in the UK. The calculator lets you choose either.
Can I calculate diesel costs too?
Yes. Switch the fuel type to diesel and the price changes to the UK diesel average.
How do I work out pence per mile?
Divide the price per litre (in pence) by your MPG, then multiply by 4.546. At 174p a litre, a 45 MPG car costs about 17.6p a mile. The calculator shows it as cost per mile.
Does it include the drive home?
Tick “Return trip” to double the distance.
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