Guide

Fuel cost calculator

Work out what a journey costs in petrol or diesel, at the average price across the UK, your region or your postcode.

By Forecourt Prices Published Updated

Work out a journey's fuel cost

Don't know your mpg? Leave it blank and we use 44.6 mpg for a petrol car and 48.4 mpg for a diesel. They are DfT figures for an average car at about 30 mph, and faster driving changes them.

Total cost £17.50
Fuel used 10.2 L
Cost per mile 17.5p
Per person £17.50

Petrol (E10) at 171.7p a litre, the UK average across 6,893 forecourts.

Updated 6:47am on 2 November.

Most of the prices behind this average are more than 3 days old.

UK and regional averages come from our price data. We update it every 15 minutes. A postcode's average uses forecourts within 5 miles. With fewer than 5 recent prices there, it widens to 10, then 15 miles.

Most of the prices behind both averages are more than 3 days old.

Cost per mile at the latest prices

On our latest figures, a mile costs 17.5p in a petrol car doing 44.6 mpg, and 18.6p in a diesel doing 48.4 mpg.

What a mile costs at each fuel's UK average, by miles per gallon.
Fuel A litre 30 mpg 40 mpg 50 mpg 60 mpg Our mpg
Petrol (E10) 171.7p 26.0p 19.5p 15.6p 13.0p 17.5p at 44.6
Super unleaded (E5) 188.7p 28.6p 21.4p 17.2p 14.3p 19.2p at 44.6
Diesel (B7) 198.4p 30.1p 22.5p 18.0p 15.0p 18.6p at 48.4
Premium diesel 217.4p 32.9p 24.7p 19.8p 16.5p 20.4p at 48.4

"Our mpg" is 44.6 mpg for petrol and 48.4 mpg for diesel.

UK averages across 6,893 forecourts for petrol and 6,341 for diesel, from our price data. We update it every 15 minutes.

What 30, 100 and 200 miles cost

What each journey costs in fuel at the UK averages.
Miles Petrol at 44.6 mpg Diesel at 48.4 mpg
30 £5.25 £5.59
100 £17.50 £18.64
200 £35.00 £37.27

How far does £20 go?

£20 buys 11.6 litres of petrol at 171.7p a litre. At 44.6 mpg, that is about 114 miles. In diesel at 198.4p, £20 buys 10.1 litres, or about 107 miles at 48.4 mpg.

How to work out fuel cost

A UK gallon is 4.54609 litres, as the Weights and Measures Act 1985 sets it[1]. Fuel is sold by the litre, but mpg counts gallons, so every sum needs that figure.

What a gallon of petrol or diesel costs at our UK averages.

  • Litres used = miles ÷ mpg × 4.54609
  • Journey cost = litres used × price a litre
  • Cost per mile = price a litre × 4.54609 ÷ mpg

Take 100 miles in a petrol car doing 44.6 mpg. That uses 100 ÷ 44.6 × 4.54609 = 10.19 litres. At the latest average of 171.7p a litre, that costs £17.50, or 17.5p a mile.

If your car shows litres per 100 km, multiply that by the kilometres and divide by 100 to get the litres. To turn mpg into litres per 100 km, divide 282.481 by the mpg. That figure comes from the same Act's gallon and mile[1].

How to work out your car's mpg

Fill the tank to the brim and set the trip counter to zero. Drive as normal, then fill to the brim again and note the litres it took. Divide those litres by 4.54609 to get gallons[1]. Then divide the miles on the trip counter by the gallons.

Is petrol or diesel cheaper per mile?

At the latest averages, diesel costs 15.6% more a litre than petrol. So a diesel car needs more than 15.6% better mpg than a petrol car to cost less per mile.

At 44.6 mpg for petrol and 48.4 mpg for diesel, a mile costs 17.5p in petrol and 18.6p in diesel. So the diesel car costs more per mile.

The answer turns on the price gap and the two cars' mpg, not on how far you drive. A fuel that is cheaper per mile stays cheaper over any number of miles.

Why diesel costs more than petrol.

What a year of driving costs

Cars in England averaged 7,100 miles in 2025, in the Department for Transport's National Travel Survey[2]. The survey covers England only, and DfT says its 2025 figures are not fully comparable with earlier years[2].

At the latest prices, 7,100 miles costs about £1,240 in petrol at 44.6 mpg, or about £1,320 in diesel at 48.4 mpg.

Fuel for a year of driving at each fuel's UK average, to the nearest £10.
Miles a year Petrol at 44.6 mpg Diesel at 48.4 mpg
7,100 (England average, 2025) £1,240 £1,320
8,000 £1,400 £1,490
12,000 £2,100 £2,240

Cost per mile by region

At 44.6 mpg, a mile of petrol costs from 16.7p in Northern Ireland to 17.7p in the South East.

Regional averages from our price data, across every forecourt in each region.

Each UK region's average petrol and diesel price, and what a mile costs, cheapest petrol mile first.
Region Petrol Petrol a mile at 44.6 Diesel Diesel a mile at 48.4
Northern Ireland, mostly from older prices 164.2p 16.7p 190.9p 17.9p
North East, mostly from older prices 170.1p 17.3p 198.1p 18.6p
Yorkshire, mostly from older prices 170.6p 17.4p 197.9p 18.6p
London, mostly from older prices 171.9p 17.5p 199.7p 18.8p
North West, mostly from older prices 172.1p 17.5p 198.1p 18.6p
Wales, mostly from older prices 171.4p 17.5p 198.0p 18.6p
East Midlands, mostly from older prices 172.6p 17.6p 198.8p 18.7p
East of England, mostly from older prices 172.4p 17.6p 198.9p 18.7p
Scotland, mostly from older prices 172.6p 17.6p 200.0p 18.8p
South West, mostly from older prices 172.4p 17.6p 199.5p 18.7p
West Midlands, mostly from older prices 172.7p 17.6p 199.3p 18.7p
South East, mostly from older prices 173.5p 17.7p 200.1p 18.8p

Figures marked † are mostly from prices over 3 days old.

Regional averages updated 6:47am on 2 November.

Supermarket forecourts average 170.0p a litre for petrol, 1.8p less than the major brands. Over 100 miles at 44.6 mpg, that is 18p less. Compare every brand's prices.

Most of the prices behind these averages are more than 3 days old.

Business mileage

HMRC sets advisory fuel rates for company cars. From 1 September 2026, the petrol rates are 14p, 17p and 27p a mile, by engine size[3]. The diesel rates are 15p, 16p and 22p a mile[3]. If you use your own car for work, your employer can pay you up to 55p a mile tax-free for the first 10,000 business miles. It is 25p after that[4]. HMRC says the changes aim to ensure the rates "better reflect the average costs of motoring"[5].

See HMRC's rates set against what fuel costs, band by band.

Common questions about fuel cost

How much is a mile of petrol?

On our latest figures, a mile of petrol costs 17.5p in a car doing 44.6 mpg, at 171.7p a litre. At 40 mpg it is 19.5p, and at 50 mpg 15.6p.

How much does 100 miles of petrol cost?

On our latest figures, 100 miles of petrol costs £17.50 at 44.6 mpg and 171.7p a litre. At 40 mpg it is £19.51.

How far does £20 of petrol get me?

£20 buys 11.6 litres of petrol at 171.7p a litre. At 44.6 mpg, that is about 114 miles. In diesel at 198.4p, £20 buys 10.1 litres, or about 107 miles at 48.4 mpg.

How do I work out my car's mpg?

Fill the tank to the brim and set the trip counter to zero. At the next fill, brim it again and note the litres. Divide the litres by 4.54609 to get gallons[1], then divide the miles by the gallons.

How many litres in a UK gallon?

A UK gallon is 4.54609 litres. That is the legal figure in the Weights and Measures Act 1985[1].

Is diesel cheaper per mile than petrol?

At the latest averages, diesel costs 15.6% more a litre than petrol. So a diesel car needs more than 15.6% better mpg than a petrol car to cost less per mile. At 44.6 mpg for petrol and 48.4 mpg for diesel, a mile costs 17.5p in petrol and 18.6p in diesel. So the diesel car costs more per mile.

What is the average annual mileage?

Cars in England averaged 7,100 miles in 2025, in the Department for Transport's National Travel Survey[2]. At the latest prices, 7,100 miles costs about £1,240 in petrol at 44.6 mpg, or about £1,320 in diesel at 48.4 mpg.

Sources and method

  1. legislation.gov.uk: Weights and Measures Act 1985, Schedule 1, checked 15 October 2026.
  2. GOV.UK (DfT): NTS0901, Annual mileage of cars by ownership, fuel type and trip purpose: England, checked 15 October 2026.
  3. GOV.UK (HMRC): Advisory fuel rates, checked 16 October 2026.
  4. GOV.UK: Expenses and benefits, business travel mileage for employees' own vehicles, checked 16 October 2026.
  5. HMRC: Increasing mileage rates (policy paper), checked 16 October 2026.

Our figures: each UK and regional average covers every forecourt's latest price from the last 30 days. It leaves out prices far from what the rest of the UK charges. A postcode's average uses forecourts within 5 miles. With fewer than 5 recent prices there, it widens to 10, then 15 miles. Every sum uses the legal gallon of 4.54609 litres. How we work out the figures