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    Fuel Cost Calculator

    Calculate how much fuel your journey will cost. Enter distance, fuel efficiency, and fuel price.

    Free to use. Runs in your browser.

    Enter your distance, vehicle fuel economy (MPG or L/100km), and fuel price to estimate journey cost. Works with petrol, diesel, and electric vehicles.

    General information only. These fuel-cost figures are estimates based on the distance, efficiency, and price you enter. Fuel prices change daily and vary by location, so they are not a precise budget and not financial advice. For business mileage, follow HMRC approved mileage rates and confirm with a qualified accountant.

    Methodology and sources

    Formula or method

    For MPG mode: litres used = (distance in miles / MPG) x 4.546 (UK Imperial gallon to litres). Total cost = litres used x price per litre. Cost per mile = total cost / distance. For L/100km mode: litres used = (distance in km / 100) x L/100km value. The same cost and cost-per-unit formulas then apply. All arithmetic is performed client-side; no live fuel-price data is fetched.

    Basis and assumptions

    • The UK Imperial gallon conversion factor is 4.546 litres per gallon, matching the UK statutory definition (Weights and Measures Act 1985). The US liquid gallon (3.785 L) is NOT used; the tool is calibrated for UK MPG figures.
    • The fuel price per litre is supplied entirely by the user. The default prefill of 1.57 p/litre (£1.57/L) reflects May 2026 average UK unleaded petrol prices per RAC Fuel Watch but is a static placeholder, not a live feed.
    • A single uniform fuel-price figure is applied across the entire distance. It does not model price variation between locations, supermarket vs branded forecourts, or price changes mid-journey.
    • The tool applies one efficiency figure across the whole journey. It does not model urban vs motorway driving cycles, cold-start fuel penalty, load, or tyre-pressure effects.
    • Currency selection (GBP, USD, CAD, AUD, EUR) changes the displayed symbol only; it does not convert the numeric fuel price or apply any exchange rate.
    • The L/100km branch uses the continental European standard measure. The MPG branch uses UK Imperial MPG, not US MPG (which uses the smaller US gallon and will give different results for the same numeric value).

    Key handling decisions

    • UK Imperial gallon (4.546 L) is the assumed gallon for MPG mode, matching UK vehicle specifications. US drivers quoting US-MPG figures should divide their MPG by approximately 1.201 before entering, or select L/100km.
    • Cost per unit is labelled 'per mile' in MPG mode and 'per km' in L/100km mode, consistent with the input distance unit.
    • Invalid inputs (zero, empty, non-numeric) cause the calculate function to return early with no result displayed, preventing division-by-zero.

    What this tool does not decide

    • Whether to switch from petrol or diesel to electric or hybrid. A whole-life cost comparison requires depreciation, insurance, servicing, road tax, and grant eligibility. Consult an independent financial adviser regulated by the Financial Conduct Authority (FCA) for a personalised vehicle-finance assessment.
    • Annual fuel budget for tax or accounting purposes. HMRC approved mileage rates (45p per mile for the first 10,000 miles, 25p thereafter for cars) govern business mileage claims and differ from actual fuel cost. Confirm current rates with HMRC or a qualified accountant.
    • Whether a fuel-type switch is environmentally justified. Lifecycle carbon analysis covering manufacturing emissions is outside this tool's scope; see the UK Government's car-emission figures on GOV.UK.
    • Live pump prices. The prefilled price is a static May 2026 snapshot. Always verify current prices at RAC Fuel Watch or the GOV.UK weekly road fuel prices report before making financial decisions.

    Sources

    Last checked: 2026-06-17

    How Fuel Costs Are Calculated

    The formula is simple: Fuel Cost = (Distance / Fuel Efficiency) x Price per Litre. If you're driving 200 miles in a car that does 40 MPG, you'll use 5 UK gallons (22.7 litres). At the May 2026 average petrol price of £1.57/litre, that's £35.69. Diesel drivers paying around £1.88/litre would pay £42.73 for the same trip at the same MPG.

    The tricky part is fuel efficiency. The number on your car's spec sheet is measured in lab conditions, real-world MPG is typically 10-20% worse. Motorway driving, cold starts, heavy loads, and aggressive driving all reduce efficiency. Use your real-world figure for more accurate results.

    To find your actual MPG: fill up completely, reset the trip counter, drive normally until you need fuel again, then divide the miles driven by the gallons used. Do this 2-3 times and average it. That's your real number.

    Average Fuel Economy by Vehicle Type

    Vehicle TypeOfficial MPGReal-World MPGCost per Mile (May 2026: petrol £1.57/L, diesel £1.88/L)
    Small hatchback (petrol)55-6545-5214-16p
    Medium saloon (petrol)45-5535-4516-20p
    SUV (petrol)35-4528-3819-25p
    Small diesel65-7550-6014-17p
    Hybrid (petrol)55-7050-6511-14p
    Plug-in hybrid (short trips)100-200+60-100+7-12p
    Electric (home charging)N/A3.5-4.5 mi/kWh5-7p

    What this means for you: At May 2026 prices, an electric car costs about 5-7p per mile on home charging vs 16-20p for a petrol saloon. Over 10,000 miles a year, that's roughly £900-£1,500 in fuel savings. Public rapid charging narrows the gap to around 14-22p per mile depending on the network. Verify the current pump price at RAC Fuel Watch or GOV.UK weekly road fuel prices, because petrol and diesel have moved significantly in 2026.

    UK Fuel Prices: Current and Recent History

    Most recent week first. The first row is the current May 2026 average. The remaining rows are historical context only and do not reflect current pump prices.

    PeriodUnleaded (p/L)Diesel (p/L)Context
    May 2026~157p~188pCurrent. Mid-2026 surge after Q1 oil supply disruption
    Jan 2026140p148pHistorical: January 2026 baseline (no longer current)
    Jan 2024143p152pHistorical: prices stabilising after 2022 spike
    Jul 2022191p199pHistorical: all-time UK high (Ukraine crisis)
    Jan 2020127p132pHistorical: pre-COVID baseline

    What this means for you: Petrol is now around £1.57/litre and diesel around £1.88/litre, well above the pre-COVID baseline. Diesel is approaching the Jul 2022 peak of 199p. Supermarket forecourts (Asda, Sainsbury's, Tesco, Morrisons) are consistently 3-5p/litre cheaper than branded stations. Over a 50-litre fill-up, that's £1.50-£2.50 saved. For the latest pump prices, RAC Fuel Watch and the GOV.UK weekly road fuel prices report are updated regularly.

    Ways to Reduce Your Fuel Bill

    Check tyre pressure monthly

    Under-inflated tyres increase rolling resistance and fuel consumption by 3-5%. Check pressures when cold and inflate to the manufacturer's recommendation (usually on a sticker inside the driver's door).

    Drive smoothly

    Aggressive acceleration and hard braking can increase fuel consumption by 15-30%. Anticipate traffic, coast to red lights, and stay in the highest gear possible. Cruise control helps on motorways.

    Remove roof boxes when not in use

    A roof box or rack increases aerodynamic drag. At motorway speeds, this can reduce MPG by 10-25%. Take it off between trips, the fuel savings add up fast.

    Use supermarket fuel

    All UK fuel meets the same BS EN 228 standard. Premium fuels offer marginal benefits for high-performance engines, but for most cars, supermarket fuel is identical in quality and 3-5p/litre cheaper.

    Petrol vs Diesel vs Electric: Real Cost Per Mile

    Fuel TypeCost Per MileAnnual Cost (10,000 miles)Notes
    Petrol (40 mpg)17-19p£1,780-£1,900Most common UK fuel type
    Diesel (50 mpg)16-18p£1,600-£1,800Better MPG offsets higher pump price
    Hybrid (55 mpg)12-14p£1,200-£1,400Depends heavily on driving style
    EV (home charging)5-7p£500-£700Off-peak tariff assumed
    EV (public charging)14-22p£1,400-£2,200Rapid chargers cost more

    What this means for you: Figures use May 2026 average pump prices (petrol £1.57/litre, diesel £1.88/litre). At those prices, an EV charged at home overnight remains the cheapest option by far, roughly a third of petrol costs. But if you rely on public rapid chargers, the savings shrink and can disappear at peak rates. The sweet spot for EVs is home charging with an off-peak energy tariff. Pump prices change frequently, so verify current figures before making a switching decision.

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    How to use this tool

    1

    Enter the distance of your journey in miles or kilometres

    2

    Enter your vehicle's fuel economy (MPG or L/100km)

    3

    Enter the current fuel price per litre or gallon

    Common uses

    • Calculating the fuel cost of a specific journey
    • Comparing fuel costs between different vehicles
    • Estimating annual fuel expenditure for budgeting
    • Working out cost per mile for business mileage claims
    • Comparing petrol, diesel, and electric running costs

    Share this tool

    Frequently Asked Questions

    How is fuel cost calculated?
    Fuel cost = (distance / fuel efficiency) x price per litre. For UK MPG: convert miles to gallons (distance / MPG), then gallons to litres (x 4.546), then multiply by the price per litre.
    What's an average MPG for a UK car?
    The average UK car gets around 36 MPG combined (real-world). Small hatchbacks manage 45-52 MPG, family saloons 35-45 MPG, and SUVs 28-38 MPG. Hybrids typically achieve 50-65 MPG in mixed driving.
    How do I convert MPG to L/100km?
    Divide 282.48 by the MPG value. For example, 40 MPG = 282.48 / 40 = 7.06 L/100km. Lower L/100km is better. Most European cars quote efficiency in L/100km rather than MPG.
    Why is my real MPG lower than the official figure?
    Official WLTP figures are measured in lab conditions with no wind, flat roads, and optimal temperature. Real-world driving typically achieves 10-20% less due to traffic, hills, cold starts, air conditioning, and driving style.
    How do I calculate my actual MPG?
    Fill up completely, reset your trip counter, drive normally, then fill up again at the same pump. Divide miles driven by gallons used (litres / 4.546 = gallons). Repeat 2-3 times and average the result.
    Is diesel cheaper per mile than petrol?
    Diesel engines are typically 15-20% more fuel-efficient than petrol. The fuel-price gap between diesel and petrol changes with market conditions: it has historically been 5-8p/litre but as of May 2026 diesel is around 30p/litre more than petrol due to oil supply disruption from early 2026. At that gap, diesel's better efficiency does not always offset the higher pump price. Verify current pump prices for both before assuming diesel is cheaper.
    How much does the average UK driver spend on fuel?
    The average UK driver covers 7,400 miles/year. At 36 MPG and the May 2026 average petrol price of around £1.57/litre, that is roughly £1,470/year on fuel. Higher mileage drivers (15,000 miles/year) spend closer to £2,975. Diesel drivers face higher pump prices (around £1.88/litre in May 2026) but typically get more miles per gallon. Verify the current pump price at RAC Fuel Watch or GOV.UK weekly road fuel prices before relying on these figures.
    Is it worth driving further for cheaper fuel?
    A 5p/litre saving on a 50-litre fill saves £2.50. If the cheaper station is 5 miles out of your way, the extra fuel to get there costs about 70p, so yes, it's usually worth it. But driving 20 miles? Probably not.
    Does speed affect fuel consumption?
    Significantly. Most cars are most efficient at 45-55 mph. Driving at 80 mph vs 70 mph increases fuel consumption by 10-20%. Reducing motorway speed from 80 to 65 mph can improve MPG by 15-25%.
    How much does air conditioning cost in fuel?
    AC increases fuel consumption by 5-10% in city driving. At motorway speeds, the impact drops to 2-3% because AC compressors are more efficient at higher RPM. Below 40 mph, opening windows is more fuel-efficient than AC.
    Is premium fuel worth the extra cost?
    For most cars, no. Standard fuel meets all requirements. Premium (super unleaded) offers marginal benefits for high-performance or turbocharged engines. The 10-15p/litre premium rarely delivers a measurable improvement in economy or performance for normal cars.
    How does an electric car compare on running costs?
    At off-peak home charging rates (around 7-9p/kWh on overnight EV tariffs), an EV costs roughly 2-3p per mile to run vs 17-19p for a petrol car at May 2026 average pump prices. Over 10,000 miles, that is about £200-300/year for an EV on overnight charging vs roughly £1,800/year for petrol. Standard daytime electricity rates push EV running cost closer to 5-7p per mile, and public rapid chargers in May 2026 typically work out at 14-22p per mile depending on the network.

    Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.