How do I calculate fuel cost for a trip?

Divide the trip distance by your vehicle's fuel economy (MPG or L/100km) to get fuel volume used, then multiply by the price per litre or gallon. Example: a 300-mile trip at 45 MPG uses 6.67 UK gallons; at £6.00/gal that's £40 in fuel.

What is the difference between UK MPG and US MPG?

They are different units. UK MPG uses imperial gallons (4.546 litres); US MPG uses US gallons (3.785 litres). UK MPG figures are about 20% higher than US MPG for the same car. This calculator defaults to UK MPG — switch to US MPG in the dropdown if quoting US data.

What's a good MPG for a modern car?

Modern UK figures: small petrol hatchback 50–60 MPG, family diesel 55–65 MPG, mid-size SUV 35–45 MPG, hybrid saloon 60–70 MPG, plug-in hybrid 130+ MPG (test cycle — real-world 50–80 MPG).

How much fuel does the average UK driver use per year?

The UK average is 7,400 miles per year (DfT, 2024). At an average 42 MPG and £1.46/litre petrol that's roughly £1,170 per year. Diesel drivers average 9,500 miles and £1,400 per year on fuel.

Should I convert to MPG or L/100km?

The UK uses MPG; most of continental Europe uses litres per 100 km. Conversion: L/100km = 282.5 ÷ UK MPG. So 50 UK MPG = 5.65 L/100km. This calculator shows both automatically.

⛽ Fuel Cost & MPG Calculator

Work out the fuel cost of any trip, your car's MPG / L/100km, cost per mile and your annual fuel spend.

Distance

Distance unit

Fuel economy

Economy unit

Fuel price

Price unit

Annual mileage (for yearly cost)

⛽ Real-world MPG is typically 10–20% lower than manufacturer-claimed figures. Track several tank-to-tank fills for accuracy.

How to Read MPG and L/100km

MPG (miles per gallon) measures distance per unit of fuel — higher = better. L/100km (litres per 100 km) measures fuel consumed per fixed distance — lower = better. Most UK drivers use MPG; continental Europe and most carmakers' brochures use L/100km. Conversion: L/100km = 282.5 ÷ UK MPG.

How to Improve Your Fuel Economy

Maintain tyre pressure: under-inflated tyres can cost 3% extra fuel
Steady throttle: harsh acceleration uses up to 25% more fuel
Drive at 60 mph not 70 mph on motorways: typically saves 9% fuel
Remove roof boxes when not in use: aerodynamic drag can cost 15–25% MPG
Don't carry dead weight: every 50 kg costs roughly 1–2% MPG
Service regularly: dirty air filters and old spark plugs reduce efficiency

Petrol vs Diesel — Which Pays Off?

Diesel cars typically achieve 10–20% better MPG than petrol equivalents, but pump diesel is 5–10p/litre more expensive and diesels have higher servicing costs and higher first-year VED. The break-even point is usually around 15,000 miles/year — below that, modern petrol or hybrid is cheaper to own. Pair this with our km to miles converter for European trips.

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Important Note: Manufacturer-quoted MPG (WLTP) is a laboratory figure. Real-world economy depends on driving style, terrain, weather, traffic and load. Use your own brim-to-brim measurements for the most accurate figure.

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