Fuel Cost Calculator
This fuel cost calculator estimates trip gas expenses based on distance, fuel efficiency, and price. Supports miles/km, multi-trip comparison, and round trips.
Estimate trip fuel costs by multiplying distance divided by fuel efficiency by the fuel price: a 300-mile trip at 30 MPG with petrol at $4.15/gallon costs 10 gallons, or about $41.50. The calculator supports imperial (miles, gallons, MPG) and metric (km, litres, L/100km), multi-trip budgeting for road trips, round-trip toggling, and side-by-side vehicle comparison to find the cheaper option over time.
For informational purposes only. Not financial advice. Calculations are estimates and may not reflect your exact situation. Consult a qualified financial adviser for personalised guidance.
About Fuel Cost Calculator
How Fuel Cost Is Calculated
Fuel cost equals the fuel consumed multiplied by the price per unit. Two formulas cover the world's two dominant fuel-economy conventions:
Imperial: Fuel Cost = (Distance / MPG) x Price per gallon
Metric: Fuel Cost = (Distance / 100) x L/100km x Price per litre
Worked example (Imperial): A 350-mile trip in a 28 MPG saloon with petrol at $4.15/gallon (US EIA weekly average, June 2026) needs 350 / 28 = 12.5 gallons. Total cost: 12.5 x $4.15 = $51.88. Cost per mile: $51.88 / 350 = $0.148 (14.8 cents).
Worked example (Metric): A 500 km trip at 7.5 L/100km with petrol at £1.58/litre (UK Department for Energy Security weekly average, June 2026) needs (500 / 100) x 7.5 = 37.5 litres. Total cost: 37.5 x £1.58 = £59.25. Cost per km: £59.25 / 500 = £0.119.
To convert between the two systems: L/100km = 235.215 / MPG (US) or L/100km = 282.481 / MPG (UK). The UK and US gallons are different sizes (US gallon = 3.785 litres, imperial gallon = 4.546 litres), which is why a car rated "40 MPG" in the UK is roughly 33 MPG in US terms.
Current Fuel Prices (June 2026)
UK unleaded petrol averaged 158.7p per litre in the week beginning 1 June 2026 per the UK Department for Energy Security and Net Zero weekly road-fuel statistics. In the US, the EIA's Weekly Retail Gasoline Prices report put regular unleaded at $4.15 per gallon in the week of 8 June 2026, easing from a late-May peak above $4.30. Both figures are well above their five-year averages, driven by crude oil supply tightness and higher refining margins.
| Country | Fuel | June 2026 Avg | Source |
|---|---|---|---|
| UK | Unleaded E10 (per litre) | 158.7p | UK DESNZ weekly |
| UK | Diesel (per litre) | 184.1p | UK DESNZ weekly |
| US | Regular gasoline (per gal) | $4.15 | EIA weekly |
| US | Diesel (per gal) | $5.21 | EIA weekly |
| EU | Unleaded 95 (per litre) | EUR 1.64 | European Commission Oil Bulletin (April 2026) |
Common Trip Cost Estimates
Below are reference costs based on the June 2026 averages above. Actual prices vary 10-15p/litre in the UK and $0.30-0.50/gallon in the US between stations in the same postcode/zip, so the real figure depends on where you refill.
UK drivers at 158p/litre, 40 MPG (imperial) average car:
| Journey | Approx Distance | Fuel Cost (each way) | Round Trip |
|---|---|---|---|
| London to Birmingham | 120 miles | £21.50 | £43 |
| London to Manchester | 200 miles | £35.90 | £71.80 |
| London to Edinburgh | 400 miles | £71.80 | £143.60 |
| London to Cornwall | 280 miles | £50.25 | £100.50 |
| Daily commute (15 miles) | 30 miles/day | £5.40/day | £27/week |
US drivers at $4.15/gallon, 28 MPG:
| Journey | Approx Distance | Fuel Cost (each way) | Round Trip |
|---|---|---|---|
| NYC to Washington DC | 225 miles | $33.35 | $66.70 |
| LA to San Francisco | 380 miles | $56.32 | $112.64 |
| Chicago to Detroit | 280 miles | $41.50 | $83.00 |
| Denver to Salt Lake City | 525 miles | $77.81 | $155.62 |
| Daily commute (20 miles) | 40 miles/day | $5.93/day | $29.65/week |
What Does a Daily Commute Actually Cost Per Year?
Assume 48 working weeks (52 minus holidays and sick days) and a five-day week. A 30-mile daily round trip in an average petrol car burns roughly £1,300/year in fuel at UK June 2026 prices. Double that commute and the annual bill passes £2,500. The table below runs the numbers at both UK and US averages so housing and job-offer decisions can factor the real cost in.
| Daily Round Trip | Annual Distance | UK Cost (40 MPG, 158p/L) | US Cost (28 MPG, $4.15/gal) |
|---|---|---|---|
| 10 miles | 2,400 miles | £432 | $356 |
| 20 miles | 4,800 miles | £863 | $711 |
| 30 miles | 7,200 miles | £1,295 | $1,067 |
| 50 miles | 12,000 miles | £2,158 | $1,779 |
| 80 miles | 19,200 miles | £3,452 | $2,846 |
These numbers do not include insurance, vehicle excise duty, maintenance, or depreciation, which typically add another £2,000-£3,500 per year for a mid-size car according to the RAC Cost of Motoring report. Fuel is usually the second-largest motoring cost after depreciation.
What Reduces Fuel Consumption the Most?
Driving at moderate speed is the single biggest lever. The US Department of Energy (fueleconomy.gov) reports fuel economy drops by 7% when speed rises from 60 to 65 mph and by around 14% from 55 to 65 mph - every 5 mph above 50 mph effectively adds 14-20 cents per gallon at current prices.
- Steady highway speed: Cruise control on motorways/highways saves fuel versus throttle-and-coast human driving.
- Smooth acceleration: Aggressive driving (hard starts, sudden braking) lowers economy by 15-30% on highways and 10-40% in town per the US DoE.
- Tyre pressure: Underinflated tyres cut MPG by about 0.2% per 1 psi below the recommended figure (DoE). Check pressure monthly when cold.
- Reduce load and drag: Every 100 lbs (45 kg) of extra weight cuts MPG by around 1%. Empty roof boxes add 10-25% drag at motorway speed even when not loaded - remove when unused.
- Combine errands: A cold engine uses up to twice as much fuel as a warm one in the first 5-10 minutes. One long trip burns less than several short cold starts.
- Shop around for fuel: PetrolPrices (UK) and GasBuddy (US) map nearby pump prices. A 10p/litre difference on a 50-litre fill is £5 saved; on 20,000 miles/year that is roughly £100-£150.
Petrol vs Diesel vs Electric: Annual Running Cost
At 10,000 miles a year with June 2026 UK energy prices (Ofgem price cap unit rate of 24.67p/kWh for home charging), an average electric car costs well under half as much to fuel as the same-class petrol car. Public rapid charging at 75-85p/kWh can push EV running costs above petrol in the worst cases.
| Powertrain | Efficiency | Energy Price | Annual Fuel (10k miles) |
|---|---|---|---|
| Petrol (average car) | 40 MPG | 158p/L | £1,795 |
| Diesel | 50 MPG | 184p/L | £1,674 |
| Hybrid | 55 MPG | 158p/L | £1,305 |
| EV (home charging) | 3.5 mi/kWh | 24.67p/kWh | £705 |
| EV (public rapid) | 3.5 mi/kWh | 80p/kWh | £2,286 |
The electricity cost calculator gives precise EV charging estimates at your own kWh price. For swapping units between systems, the km to miles converter handles the distance side, and the gas mileage calculator works out MPG from distance and fuel used.
Common Mistakes Drivers Make With Fuel Cost Estimates
- Using the car's quoted MPG instead of real-world figures. WLTP figures on the manufacturer spec sheet are 10-20% better than everyday driving. Always use your own measured MPG from the last few fills.
- Ignoring the UK vs US gallon difference. A US importer reading "45 MPG" on a UK car will overpay for fuel: that car is closer to 37 MPG in US gallons.
- Forgetting round-trip distance on errands. Typing in 15 miles for a 15-mile-each-way commute halves the real cost - the round-trip toggle prevents this.
- Comparing only pump price. A supermarket pump 3p/litre cheaper 10 miles out of the way may cost more in fuel than it saves.
- Assuming diesel is always cheaper. Diesel fuel is usually 5-30p/litre more than petrol in the UK (currently around 25p higher per DESNZ June 2026 weekly data), so the better MPG needs to cover that premium before savings start.
All calculations run in your browser. No data is stored or transmitted.
Sources
Frequently Asked Questions
How do I calculate fuel cost for a road trip?
Divide the total trip distance by your vehicle's fuel efficiency (MPG or km/L), then multiply the result by the current fuel price per gallon or liter. For example, a 300-mile trip in a car averaging 30 MPG with gas at $3.50/gallon would need 10 gallons, costing $35.00.
What is the difference between MPG and L/100km?
MPG (miles per gallon) is used in the US and UK, where higher numbers mean better efficiency. L/100km (liters per 100 kilometers) is the metric standard used in most other countries, where lower numbers indicate better efficiency. A car getting 30 MPG is roughly equivalent to 7.84 L/100km.
How does the round trip option work?
Enabling the round trip toggle doubles the distance for your calculation. This is useful when planning a trip where you need to drive back the same route, so you can see the total fuel cost for both directions at once.
Can I compare fuel costs for multiple trips?
Yes. Use the multi-trip feature to add several trips with different distances, fuel efficiencies, and prices. The calculator shows individual costs for each trip plus a combined total, which is helpful for planning a multi-stop road trip or comparing commute routes.
How can I improve my vehicle's fuel efficiency?
Maintain proper tire pressure, drive at moderate speeds, avoid aggressive acceleration and braking, remove excess weight from the vehicle, use cruise control on highways, keep the engine properly maintained, and combine short trips when possible.
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