Fuel cost calculator
Work out what a journey or a fill-up costs at today's UK fuel prices. Petrol averages 174.2p a litre and diesel 199.2p (updated 17:30 today). A 100-mile trip in a 45 mpg petrol car costs about £17.60.
Cost of 100 miles at today's prices
UK average prices: petrol 174.2p, diesel 199.2p.
| Fuel economy | Petrol | Diesel | Petrol per mile |
|---|---|---|---|
| 30 mpg | £26.40 | £30.19 | 26.4p |
| 40 mpg | £19.80 | £22.64 | 19.8p |
| 50 mpg | £15.84 | £18.11 | 15.8p |
| 60 mpg | £13.20 | £15.09 | 13.2p |
Cost to fill up today
| Tank | Petrol | Super unleaded | Diesel |
|---|---|---|---|
| 40 litres | £69.68 | £76.68 | £79.68 |
| 50 litres | £87.10 | £95.85 | £99.60 |
| 60 litres | £104.52 | £115.02 | £119.52 |
| 70 litres | £121.94 | £134.19 | £139.44 |
Petrol prices today · Diesel prices today · Is it worth driving further for cheaper fuel?
HMRC advisory fuel rates vs today's prices
HMRC's mileage rates for company cars from 1 September 2026 assume petrol at 159.9p and diesel at 179.2p a litre. At today's UK averages, here is what the same cars cost per mile, using HMRC's own fuel economy figures.
| Engine | HMRC rate | At today's price | Difference |
|---|---|---|---|
| Petrol, 1400cc or less | 14p | 15.6p | +1.6p |
| Petrol, 1401cc to 2000cc | 17p | 18.5p | +1.5p |
| Petrol, over 2000cc | 27p | 29.1p | +2.1p |
| Diesel, 1600cc or less | 15p | 16.3p | +1.3p |
| Diesel, 1601cc to 2000cc | 16p | 18.3p | +2.3p |
| Diesel, over 2000cc | 22p | 24.7p | +2.7p |
Rates per mile. Source: HMRC: Advisory fuel rates. The rates apply only to company cars; HMRC next reviews them on 1 December 2026.
Fuel cost questions
How do I work out the fuel cost of a journey?
Divide the distance in miles by your car's miles per gallon to get gallons, multiply by 4.546 to get litres, then multiply by the price per litre. A 100-mile trip at 45 mpg uses 10.1 litres; at today's UK average petrol price of 174.2p that costs £17.60.
How much does petrol cost per mile?
At today's UK average of 174.2p a litre, petrol costs 19.8p a mile in a car doing 40 mpg and 15.8p a mile at 50 mpg. Diesel at 199.2p costs 18.1p a mile at 50 mpg.
What are the HMRC advisory fuel rates?
HMRC's mileage rates for company cars from 1 September 2026 are 14p, 17p, 27p a mile for petrol and 15p, 16p, 22p for diesel, by engine size. They assume 159.9p petrol and 179.2p diesel; at today's prices the real cost is up to 2.7p a mile higher. HMRC reviews them every quarter, next on 1 December 2026.
How many litres are in a gallon?
A UK (imperial) gallon is 4.546 litres. A US gallon is smaller, 3.785 litres, so US mpg figures look lower for the same car.
How can I cut the cost of a journey?
Fill up where fuel is cheapest before you set off: today the cheapest and dearest petrol in the UK are 51.0p a litre apart, and motorway services usually charge the most. Search by postcode for the cheapest near you, and see how to use less fuel.