How to Calculate Your Fuel Cost Per Mile (Simple Guide)

Summary

• Simple Formula: Fuel cost per mile = (Fuel price ÷ MPG) × 100. For a car doing 40 MPG at £1.45/litre, that's about 16p per mile.
• Know Your Real Costs: Understanding cost per mile helps you budget, compare cars, and make smarter fuel choices.
• Save Money: Use our fuel finder to cut your fuel costs—even 5p/litre cheaper adds up fast.

How much does it actually cost you to drive a mile? It's a question most drivers can't answer—but should.

Knowing your fuel cost per mile helps you budget for trips, compare running costs between cars, and understand where your money goes.

Good news: it's easy to calculate. Let's walk through it step by step.

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The Simple Formula

Here's how to calculate your fuel cost per mile:

Cost per mile = (Fuel price per litre × 4.546) ÷ MPG

Or in plain English:

1. Find your car's MPG (miles per gallon)
2. Look up the current fuel price per litre
3. Convert litres to gallons (multiply by 4.546)
4. Divide to get cost per mile

Quick Example

Let's say your car does 40 MPG and petrol costs £1.45 per litre:

• Cost per gallon = £1.45 × 4.546 = £6.59
• Cost per mile = £6.59 ÷ 40 = 16.5p per mile

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Quick Reference: Fuel Cost Per Mile

Here's a handy table based on current average fuel prices (£1.45/litre petrol, £1.50/litre diesel):

Find your MPG, and you've got a quick estimate of your fuel cost per mile.

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How to Find Your Actual MPG

Your car's advertised MPG is tested in lab conditions. Real-world MPG is usually 10-20% lower. Here's how to find your actual figure:

Method 1: Check Your Dashboard

Most modern cars show "average MPG" on the dashboard display. This is usually fairly accurate—reset it and check after a week of normal driving.

Method 2: Calculate It Yourself

1. Fill your tank completely
2. Reset your trip meter to zero
3. Drive normally until you need fuel again
4. Fill up again and note how many litres you used
5. Calculate: Miles driven ÷ (Litres used ÷ 4.546) = MPG

Example: You drove 300 miles and used 35 litres.

• Gallons used = 35 ÷ 4.546 = 7.7 gallons
• MPG = 300 ÷ 7.7 = 39 MPG

For more tips on improving your MPG, see our fuel efficiency guide.

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Typical Cost Per Mile by Car Type

Different vehicles have very different running costs. Here's what you might expect:

*EV cost based on home charging at ~28p/kWh. Public charging costs more.

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Why Knowing Your Cost Per Mile Matters

Understanding your fuel cost per mile is useful for:

1. Budgeting for Trips

Planning a 200-mile journey? At 16p per mile, you'll spend about £32 on fuel. No more guessing.

2. Comparing Cars Before Buying

A car with 35 MPG costs about 19p per mile. One with 50 MPG costs 13p. Over 10,000 miles, that's £600 difference per year.

When buying a used car, factor fuel costs into your total cost of ownership.

3. Claiming Mileage Expenses

If you use your car for work, HMRC allows you to claim 45p per mile for the first 10,000 miles (25p after that). Knowing your actual cost helps you understand your real profit.

4. Deciding Whether to Drive or Take the Train

A 100-mile trip at 16p/mile = £16 in fuel. Is that cheaper than a train ticket? Now you can compare properly.

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How to Calculate Fuel Cost for a Trip

Planning a journey? Here's how to estimate your fuel cost:

Trip fuel cost = Distance in miles × Cost per mile

Example: London to Manchester

• Distance: 200 miles
• Your car: 40 MPG
• Your cost per mile: 16.5p
• Trip cost: 200 × 16.5p = £33

Return Journey

Don't forget to double it for a return trip! That London-Manchester journey would cost £66 for the round trip.

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How to Reduce Your Fuel Cost Per Mile

There are two ways to lower your cost per mile:

1. Pay Less Per Litre

Use our fuel finder to find the cheapest fuel near you. Saving 10p per litre reduces your cost per mile by about 1p. Over 10,000 miles, that's £100 saved.

2. Improve Your MPG

Better driving habits can boost your MPG by 15-20%:

• Accelerate gently
• Maintain steady speeds
• Keep tyres properly inflated
• Remove unnecessary weight
• Use cruise control on motorways

See our full guide on improving fuel efficiency.

Combined Effect

If you improve MPG from 35 to 42 (a 20% improvement) AND save 10p per litre on fuel:

• Old cost per mile: 18.8p
• New cost per mile: 14.5p
• Savings: 4.3p per mile = £430 per 10,000 miles

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Calculating Your Annual Fuel Cost

Want to know your yearly fuel spend? Here's the formula:

Annual fuel cost = Miles per year × Cost per mile

Example: Average UK Driver

• Average UK mileage: 7,400 miles/year
• Cost per mile (40 MPG car): 16.5p
• Annual fuel cost: 7,400 × 16.5p = £1,221

High Mileage Driver

• Mileage: 15,000 miles/year
• Cost per mile: 16.5p
• Annual fuel cost: £2,475

High-mileage drivers benefit most from fuel savings. Even 2p per mile saved = £300 per year at 15,000 miles.

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Petrol vs Diesel: Which Costs Less Per Mile?

Diesel cars typically achieve better MPG, but diesel fuel costs more. So which is cheaper per mile?

Quick Comparison

In this example, diesel is 2.6p per mile cheaper. Over 10,000 miles, that's £260. But remember—diesel cars often cost more to buy, service, and tax. For a full comparison, see petrol vs diesel.

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Electric vs Petrol: Cost Per Mile Comparison

Electric vehicles have transformed running costs. Here's how they compare:

EVs are about half the cost to run per mile. But remember: public charging is more expensive (often 50-80p/kWh), which reduces the savings. Learn more in our electric car guide.

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The Bottom Line

Calculating your fuel cost per mile is simple and incredibly useful:

1. Find your real MPG—use your dashboard display or calculate manually
2. Apply the formula: (Price per litre × 4.546) ÷ MPG = cost per mile
3. Use it for budgeting: Trip cost = miles × cost per mile

To reduce your cost per mile:

• Find cheaper fuel using our fuel finder
• Improve your MPG with better driving habits
• Consider fuel costs when choosing your next car

Small improvements add up. Just 2p per mile saved = £200 on 10,000 miles. Now you have the knowledge to make it happen!

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