How much does it cost to drive 100 miles in the UK in 2026?

It depends on your car and fuel type. A medium petrol car doing 45 MPG costs around £15.82 to drive 100 miles at current prices. An EV on home charging costs just £6.17 for the same distance. A petrol SUV doing 30 MPG costs around £23.74.

Is petrol or diesel cheaper to run?

Petrol costs less per litre, 157p versus 189.8p for diesel. But diesel cars typically get 15 to 20% better MPG. For drivers doing over 12,000 miles a year on motorways, diesel usually works out cheaper overall. For lower mileage or mostly city driving, petrol is generally the better choice.

How do I work out my car's MPG?

Fill up your tank and reset your trip counter. Drive normally until your next fill-up. Divide the miles driven by the litres of fuel added, then multiply by 4.546. That gives your MPG for that period. It is the most accurate way to know your real-world efficiency.

Can I claim fuel costs back from HMRC?

Yes, if you use your own car for work trips, you can claim up to 45p per mile for the first 10,000 miles each tax year. This covers all business journeys except your regular commute to a fixed workplace.

Are EVs really cheaper per mile than petrol cars?

On home charging, yes, significantly. At 24.67p per kWh and 4 miles per kWh, an EV costs around 6p per mile. A petrol car at 157p per litre doing 45 MPG costs around 15.8p per mile. On public rapid charging at 76p per kWh, the EV cost rises to around 19p per mile, roughly matching or exceeding petrol.

How do I find out my car's MPG?

Most modern cars have a digital dashboard display that shows your average MPG. Alternatively, you can search your exact make, model, and year online to find the manufacturer's official combined MPG rating.

Why do we use MPG but buy fuel in litres?

It's an idiosyncrasy of the UK! We measure road distances in miles and historically used gallons (Miles Per Gallon). However, fuel is now sold in metric litres. This calculator bridges the gap automatically, knowing that exactly 4.54609 litres make up a UK gallon.

Does having passengers increase fuel consumption?

Yes, slightly. More weight in the car means the engine has to work harder. As a general rule of thumb, fuel consumption increases by about 1-2% for every 50kg of extra weight. So four adult passengers with luggage will noticeably reduce your MPG compared to driving alone.

Is motorway driving more fuel efficient?

Generally, yes. Cruising at a steady 60-70mph in top gear is highly efficient compared to stop-start city driving where you constantly accelerate in lower gears. However, driving aggressively at 80mph+ drastically reduces efficiency due to wind resistance.

Automotive

Journey Cost Calculator UK

Whether you are planning a long road trip or just working out your daily commute cost, our free Journey Cost Calculator gives you an instant fuel estimate. Enter your distance, MPG and fuel type, and find out exactly what the journey will cost you.

Trip Details

Distance (One-Way)

miles

Number of People in Car

Car Fuel Economy (MPG)

MPG

UK avg is ~40-50 MPG

Fuel Price

£per litre

Estimated Total Fuel Cost£43.95

Total Distance300 mi

Litres Needed30.3 L

Gallons Needed6.7 gal

Cost Per Mile£0.15

How to Calculate Your Trip Costs

Whether you're heading off on a staycation from London to Cornwall, or just trying to calculate the actual cost of your daily commute, figuring out fuel prices can feel like solving a puzzle thanks to the UK's mix of metric and imperial measurements.

The Math Explained

To calculate your journey cost manually, you need to navigate the fact that your car's efficiency is measured in Miles Per Gallon (MPG), but fuel is sold in Litres.

1. Divide your total miles by your MPG to get Total Gallons needed.
2. Multiply the Total Gallons by 4.546 (the number of litres in a UK gallon) to find total Litres.
3. Finally, multiply the Litres by the price of fuel per litre.

Tips for Improving Fuel Economy on Long Trips

If you want to reduce how much you spend at the pump during your trip, follow these simple guidelines:

Check your tyre pressure: Under-inflated tyres increase rolling resistance. Simply pumping your tyres to the correct pressure can improve MPG by up to 3%.
Remove roof boxes and racks: Aerodynamic drag is the biggest enemy of fuel efficiency at motorway speeds. An empty roof box will dramatically reduce your MPG. Take it off if you don't absolutely need it.
Drive smoothly: Anticipate traffic flow to avoid heavy braking and harsh acceleration. Maintaining a steady pace is far more efficient than constantly accelerating and decelerating.
Use Air Con wisely: At low speeds (around town), open windows instead of using A/C. But at motorway speeds, open windows create too much drag, making the A/C the more efficient choice.

Trip Cost FAQs

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How to Use This Calculator

Enter the journey distance in miles
Select your vehicle type or enter your own MPG figure
Choose your fuel type, petrol, diesel or electric
Enter the current price per litre or per kWh
Click Calculate

Your result shows the total fuel cost, cost per mile and the amount of fuel your journey will use.

How Journey Fuel Cost Is Calculated

The formula behind the calculator is straightforward.

For petrol and diesel:

Fuel cost = (Distance ÷ MPG) × 4.546 × price per litre

The 4.546 converts gallons to litres using the UK imperial gallon. The result is your journey cost in pounds.

Example: A 200-mile trip in a car doing 45 MPG with petrol at 157p per litre:

(200 ÷ 45) × 4.546 × 1.57 = £31.78

For electric vehicles:

Fuel cost = (Distance ÷ miles per kWh) × price per kWh

Example: A 200-mile trip in an EV doing 4 miles per kWh with home charging at 24.67p:

(200 ÷ 4) × 0.2467 = £12.34

Current UK Fuel Prices : June 2026

These are the latest average UK fuel prices as of June 2026:

Fuel Type	Average Price
Unleaded petrol	157.0p per litre
Diesel	189.8p per litre
Electric (home charging)	24.67p per kWh
Electric (public rapid charging)	76.0p per kWh
Motorway service stations typically charge 15 to 25p more per litre than local supermarket forecourts. Filling up before you join the motorway can save you £8 to £12 on a full tank.

Supermarket fuel from Tesco, Asda, Sainsbury's and Morrisons is usually 3 to 8p per litre cheaper than branded stations.

Cost to Drive 100 Miles : Petrol, Diesel and Electric

Here is a quick comparison of what 100 miles costs at current UK prices:

Vehicle	Assumed Efficiency	Cost for 100 Miles
Small petrol car	55 MPG	£12.95
Medium petrol car	45 MPG	£15.82
Medium diesel car	55 MPG	£15.71
SUV petrol	30 MPG	£23.74
Hybrid	60 MPG	£11.89
Electric (home charging)	4 miles/kWh	£6.17
Electric (public rapid)	4 miles/kWh	£19.00
Home charging makes EVs the clear winner on cost per mile. Public rapid charging largely cancels that advantage, bringing it level with or above petrol costs on long journeys.

Real-World MPG vs Official Figures

This catches a lot of drivers out. The MPG figure on your car's spec sheet is measured under controlled lab conditions. Real-world driving always tells a different story.

Real-world MPG is typically 15 to 20% lower than the official manufacturer figure. So if your car is rated at 55 MPG on paper, you are likely getting closer to 44 to 47 MPG on actual roads.

Traffic, motorway speeds, cold weather, air conditioning and driving style all eat into your official figure. Our calculator uses realistic MPG profiles for each vehicle type. But entering your own observed MPG, which you can check from your trip computer or last few fill-ups, will give you the most accurate result.

Splitting Journey Costs Between Passengers

If you are travelling with others, splitting fuel costs fairly is simple.

Just divide the total journey cost by the number of people sharing the car, including yourself.

Example: A 300-mile round trip costs £47.50 in fuel. Split between four people, each person pays £11.88.

Many people use apps like Splitwise to track shared costs on longer trips. But the calculator above gives you the number to work from in the first place.

This is especially useful for regular commutes or airport runs where you share driving costs with colleagues or friends.

HMRC Mileage Rate : Claiming Back Journey Costs

If you use your own car for work travel, you can claim back the cost from your employer, or directly from HMRC through Self Assessment.

The current HMRC Approved Mileage Allowance Payment (AMAP) rates for 2026/27 are:

Vehicle	First 10,000 miles	Above 10,000 miles
Car or van	45p per mile	25p per mile
Motorcycle	24p per mile	24p per mile
Bicycle	20p per mile	20p per mile
These rates are designed to cover fuel, wear and tear and insurance. If your employer pays you less than the AMAP rate, you can claim the difference through HMRC tax relief.

Electric vehicle drivers can also claim the full 45p rate, even though their actual fuel cost per mile is considerably lower.

Tips to Spend Less on Every Journey

A few straightforward habits make a real difference to what you spend.

Drive smoothly: Gentle acceleration and anticipating the road ahead can improve your real-world MPG by 20 to 30%. Harsh braking wastes the energy you already paid for.

Keep to 60 to 65 mph on motorways: Driving at 70 mph uses around 9% more fuel than 60 mph. At 80 mph, fuel consumption rises by 25%.

Check tyre pressure monthly: Tyres 20% below their recommended pressure waste 3 to 5% extra fuel.

Remove roof boxes when not in use: A roof box adds significant aerodynamic drag, reducing MPG noticeably even on short trips.

Compare prices before you fill up. Use sites like PetrolPrices.co.uk to find the cheapest fuel near you. A difference of 10p per litre on a 50-litre fill-up saves £5 per tank, that adds up over a year.

Related Calculators

Electricity Cost Calculator UK
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Car Insurance Calculator UK

References

PetrolPrices.co.uk. Journey Cost Calculator UK 2026 , Fuel Prices and Efficiency Data. petrolprices.co.uk, June 2026
HMRC. Approved Mileage Allowance Payments, AMAP Rates 2026/27. gov.uk
RAC. UK Fuel Watch, Average Petrol and Diesel Prices June 2026. rac.co.uk
Energy Saving Trust. Fuel-Efficient Driving, Tips to Save on Every Journey. energysavingtrust.org.uk

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Frequently Asked Questions

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