How to compare UK petrol and diesel costs before a journey

Business & Money Desk 2026-10-16 08:42 3 min read

A traditional UK petrol station with vintage fuel pumps at a local garage.

A 200-mile return journey in a car averaging 40 miles per gallon uses about 5 UK gallons, or 22.7 litres. At a forecourt price of £1.50 per litre, that fuel would cost about £34.05. The example shows how to estimate your trip; the price on your chosen pump may differ from the UK weekly average.

Check the latest UK weekly fuel-price release

The Department for Energy Security and Net Zero publishes weekly UK average retail prices for petrol and diesel in its weekly road fuel prices series. Use the latest dated release as a benchmark for comparing fuel types and tracking the national picture.

The source material available does not include the latest release date or its petrol and diesel figures, so no current averages or week-on-week change are stated here. Check the collection before travelling and note the reporting week shown on the release; a weekly average describes that period, not necessarily today’s price at a particular station.

Estimate the fuel cost of your route

Use the distance for the whole journey, including the return leg if you are coming back. Then work out how much fuel the vehicle is likely to use and multiply that amount by the price displayed at the forecourt you plan to use.

For a vehicle rated in miles per UK gallon, the calculation is:

Journey cost = distance in miles ÷ miles per gallon × 4.546 × price per litre

How to compare UK petrol and diesel costs before a journey

For example, a 200-mile return trip in a vehicle averaging 40 miles per UK gallon requires about 5 gallons. Since one UK gallon is about 4.546 litres, that is roughly 22.7 litres. At an assumed pump price of £1.50 per litre, the estimate is 22.7 × £1.50, or £34.05.

The £1.50 figure is an illustrative forecourt price, not a reported UK average. Replace it with the price displayed at your chosen station. If your vehicle shows consumption in miles per gallon, check that it means UK gallons; US gallons are smaller and produce a different calculation.

Why your local pump price may differ

The government’s weekly figure is a national average. It cannot tell you what a specific forecourt charges, and prices can vary between locations and stations. The weekly release is useful for context, but the pump price is the relevant figure for estimating a fill-up at your chosen stop.

Your actual fuel use can also differ from the vehicle’s stated or usual consumption. Traffic, speed, load, weather and route conditions may affect mileage, so treat the result as a planning estimate rather than a guaranteed bill.

Before setting off, check the latest dated government release for the reporting week and compare it with the price shown by the forecourt you intend to use. Recalculate with your route distance and realistic fuel consumption; a new weekly release or a changed pump price would alter the comparison.

Source: UK Department for Energy Security and Net Zero

Context & actions About this article

Source check Price and calculation note

The government series gives weekly UK averages; the journey example uses an illustrative pump price and stated fuel consumption.

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