Fuel Cost Calculator

How the Fuel Calculator Works

The fuel calculator needs 3 inputs: distance, fuel economy and fuel price. Distance goes in as miles or kilometres. Economy can be US MPG, UK MPG or litres per 100 kilometres (L/100km), and the price box takes dollars per gallon or pence per litre, depending on which side of the Atlantic you fill up. Mix the units and you’re out by 20%. A US gallon holds 3.785 litres, while the imperial gallon used in the UK holds 4.546 litres.

The calculator returns 4 outputs: total fuel cost, fuel used in gallons and litres, cost per mile and cost per kilometre.

How to Compute Gas Cost and Diesel Cost for a Trip

To compute gas cost, divide trip miles by MPG and multiply the result by the price per gallon. UK drivers need one extra step, because pumps there price fuel by the litre.

• US formulaFuel cost = (miles ÷ US MPG) × price per US gallon
• UK formulaFuel cost = (miles ÷ UK MPG) × 4.546 × price per litre
• Metric formulaFuel cost = (km × L/100km ÷ 100) × price per litre
• Cost per milePrice per gallon ÷ MPG

Cost per mile is the figure carriers price freight against. The American Transportation Research Institute (ATRI) put the industry-average cost of running a truck at $2.336 per mile in 2025, with fuel making up about $0.482 of that. Diesel prices push that fuel line up or down every week.

Journey Fuel Cost Calculator Example: US Semi Truck

A 1,000-mile run at 7.0 MPG costs $571.43 in diesel at $4.00 per gallon. The truck burns 142.9 US gallons (541 litres) over 1,609 km, which works out to about 57 cents a mile. MPG moves the total as much as price does. Newer Class 8 tractors now run above 7.0 MPG, but an older rig returning 6.0 MPG pushes the same trip to $666.67.

UK Haulage Example: London to Glasgow in a 44-Tonne Artic

A 410-mile London to Glasgow run costs about £337 in diesel at 8.3 UK MPG and 150p per litre. The Road Haulage Association (RHA) treats 8.3 MPG as its standard planning figure for a 44-tonne articulated lorry. Over 660 km, the lorry burns 49.4 imperial gallons, or 224.6 litres, and each mile costs about 82p. VAT-registered hauliers reclaim the 20% value added tax (VAT), which brings the net bill down to roughly £281.

Fuel Cost Calculator UK: What Makes Up the Price Per Litre

A UK litre of diesel or petrol carries 4 cost layers: product cost, fuel duty, retailer margin and 20% VAT. Tax accounts for a large share. Fuel duty is fixed at 52.95p per litre until 31 December 2026, and VAT then applies to the whole duty-inclusive price. That stacking means motorists pay VAT on top of the duty itself.

Pump prices shift weekly with oil markets and the pound-to-dollar exchange rate. A fuel cost calculator UK hauliers rely on needs a fresh pence-per-litre input every week, or the quote goes stale before the lorry leaves the yard.

How Much Is a Gallon of Petrol? Cost of Petrol UK vs US Gas

A gallon of petrol costs the price per litre multiplied by 4.546 in the UK, so 140p per litre equals £6.36 per gallon. That figure applies to the imperial gallon. US gas stations sell a smaller unit, so $3.50 per US gallon works out to about 92 cents per litre.

Filling a car shows the cost of petrol UK drivers face. A 55-litre tank at 140p per litre comes to £77.

Petrol Fuel Cost Calculator for Cars and Vans

The petrol fuel cost calculator runs the same formula, using car-level MPG and petrol prices. Only the inputs shrink. Heavier vehicles follow a steep curve, as the benchmark figures below show.

Fleet benchmarks put a 7.5-tonne rigid at about 12 MPG, and the remaining rows convert from the figures sourced elsewhere in this guide.

Petrol Calculator Example: 100 Miles in a Family Car

A 100-mile trip in a 45 UK MPG petrol car costs £14.14 at 140p per litre. It burns 10.1 litres (2.2 imperial gallons), so each mile costs about 14.1p. A US car rated 30 MPG covers the same 161 km on 3.33 gallons and spends $11.67 at $3.50 per gallon. Use your trip computer’s figure rather than the brochure’s. Lab-tested MPG usually beats real-world results by 15 to 20%.

5 Hidden Fuel Costs Most Calculators Skip

Idling, empty miles, DEF, fuel surcharges and fuel tax reporting all change what a truck truly spends on fuel. Consumer calculators ignore every one of them.

• Idling: A heavy-duty truck burns roughly 0.8 US gallons (3 litres) an hour at idle, and a typical long-haul rig idles around 1,800 hours a year, using about 1,500 gallons (5,678 litres).
• Empty miles: Divide fuel cost by loaded miles, not total miles. Industry analysis often assumes 16.5% deadhead, and at that rate 57 cents of fuel per mile becomes 68 cents per paid mile.
• Diesel exhaust fluid (DEF): Trucks fitted with selective catalytic reduction (SCR) dose DEF, sold as AdBlue in the UK, at about 2 to 3% of diesel volume. A 541-litre trip needs roughly 11 to 16 litres.
• Fuel surcharge (FSC): Carriers bill (current diesel price − base price) ÷ MPG for every mile. With a $1.25 base and 6.0 MPG, $4.00 diesel produces a 46-cent surcharge per mile. Most surcharge schedules run off the EIA weekly on-highway diesel index.
• International Fuel Tax Agreement (IFTA): US and Canadian interstate carriers file quarterly returns listing miles and gallons for each jurisdiction. It applies to vehicles with 2 axles and a gross weight above 26,000 lb (11,793 kg), and to any vehicle with 3 or more axles.

How to Lower Your Fuel Cost Per Mile

To lower fuel cost per mile, raise MPG and cut the price paid per gallon. Small MPG gains add up quickly. A 44-tonne truck covering 75,000 miles a year at 7.5 MPG instead of the 8.3 MPG baseline burns 4,382 extra litres (964 imperial gallons), worth about £5,480 at 125p per litre before VAT.

• Cut idle hours: Fit an auxiliary power unit (APU) or battery HVAC system. Some idling alternatives burn up to 95% less fuel.
• Check tyre pressures weekly: Running tyres 20% below the recommended pressure wastes 3 to 5% of fuel.
• Shop around for fuel: Supermarket forecourts such as Tesco and Asda usually sell fuel 3 to 8p per litre cheaper than branded stations, which helps van and car fleets. Truck operators get similar savings through fuel card networks.
• Plan backhauls: Fewer empty miles cut fuel spend per paid mile, and that line is the one shippers pay you for.

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