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How do I work out how much fuel a trip will cost?

Enter the trip distance, your car’s fuel efficiency and the fuel price in AnyTool Fuel Cost Calculator and it works out the fuel needed and the total cost live. The maths is fuel needed = distance ÷ efficiency, then cost = fuel × price. It accepts every common convention — kilometres or miles, US MPG, UK MPG, km/L or L/100km, and a price per litre or per gallon — by normalising everything to litres-per-kilometre internally, with L/100km handled correctly as the reciprocal of km/L. A round-trip toggle doubles the distance, a people field splits the cost, and a commute mode turns a daily drive into weekly, monthly and yearly fuel spend. It is honest that real consumption varies with traffic, load, AC, terrain and driving style, and that pump prices change. Everything runs in your browser.

  • Fuel needed = distance ÷ efficiency; cost = fuel × price per litre
  • Units: km/miles · US MPG, UK MPG, km/L, L/100km · per litre or per gallon
  • Round-trip toggle, split between N people, and a commute projection
  • Shows fuel in litres and gallons, cost per km/mile and per person
  • 100% in your browser — no upload, no signup, works offline

What is

Fuel (trip) cost

Fuel cost is the money spent on petrol or diesel to cover a given distance, found by dividing the distance by the vehicle’s fuel efficiency to get the volume of fuel used, then multiplying by the price per unit of fuel. Because efficiency is expressed differently around the world — miles per gallon (US or UK), kilometres per litre, or litres per 100 km — and fuel is priced per litre or per gallon, a correct calculation normalises these to a single base, such as litres per kilometre, before multiplying by the fuel price. L/100km is the reciprocal of km/L: a lower L/100km means a more economical vehicle.

Calculators

Related terms

Fuel efficiencyMiles per gallonLitres per 100 kmCost per mileRound tripCost per person

Frequently Asked Questions

Divide the distance by the fuel efficiency to get the fuel used, then multiply by the fuel price. 300 miles at 25 MPG and $3.80/gal is 12 gal × $3.80 = $45.60.

To find a trip’s fuel cost, work out the fuel used as distance ÷ efficiency, then multiply by the price of fuel. For example, 300 miles in a car doing 25 MPG needs 300 ÷ 25 = 12 gallons; at $3.80 per gallon that is 12 × $3.80 = $45.60. In metric terms, 250 km at 7.5 L/100km uses 250 × 7.5 ÷ 100 = 18.75 L, and at $1.35/L that is about $25.31. AnyTool Fuel Cost Calculator does this live and accepts any unit — km or miles, MPG, km/L or L/100km, per litre or per gallon.

They are reciprocals: L/100km = 100 ÷ (km/L). So 15 km/L is 100 ÷ 15 ≈ 6.67 L/100km.

Kilometres per litre and litres per 100 km measure the same thing in opposite directions, so you convert with L/100km = 100 ÷ (km/L), and likewise km/L = 100 ÷ (L/100km). For example 15 km/L equals 100 ÷ 15 ≈ 6.67 L/100km, and 8 L/100km equals 12.5 km/L. A higher km/L is better while a lower L/100km is better. AnyTool handles this conversion automatically, so you can enter your efficiency in whichever unit you know and still get the right cost.

Yes. A round-trip toggle doubles the distance, and a people field divides the total fuel cost between everyone in the car.

AnyTool Fuel Cost Calculator has a round-trip toggle that doubles the one-way distance so you see the full there-and-back cost, and a people field that splits the total fuel cost evenly between passengers — handy for carpools and shared road trips. It also shows the fuel needed in litres and gallons, the cost per kilometre or mile, and the trip’s L/100km, plus an optional commute mode that projects a daily drive into weekly, monthly and yearly fuel spend.

Because real consumption varies with traffic, load, AC, hills, weather and driving style — often 10–30% above a steady figure — and pump prices change.

The calculator assumes one steady fuel-economy figure for the whole trip, but real-world consumption swings: stop-start traffic, a heavy load or roof box, air conditioning, hills and headwinds, cold starts, low tyre pressure and aggressive driving each push fuel use up, often by 10–30%, and short urban trips are thirstier than steady motorway cruising. Manufacturer or window-sticker economy is usually optimistic, so use the mileage your own car actually achieves. Fuel prices also move day to day and station to station. Treat the figure as a solid budgeting estimate and pad it for a long or hilly trip.

Detailed Explanation

Methodology

How the Fuel Cost Calculator Works

A trip’s fuel cost is computed as fuel used = distance ÷ efficiency, then cost = fuel × price. To stay correct across conventions, every fuel-efficiency unit is normalised to litres per kilometre (L/km): US MPG → L/km = 3.785411784 ÷ (mpg × 1.609344); UK MPG → L/km = 4.54609 ÷ (mpg × 1.609344); km/L → L/km = 1 ÷ (km/L); and L/100km → L/km = (L/100km) ÷ 100. Distance is converted to kilometres (1 mile = 1.609344 km) and price to per-litre (÷ 3.785411784 for US gallons, ÷ 4.54609 for UK gallons). Litres = trip-km × L/km, total cost = litres × price-per-litre, and the tool also reports cost per km/mile, cost per person and the trip’s L/100km. All of this is a pure function in a small, unit-tested engine.

  • fuel = distance ÷ efficiency; cost = fuel × price
  • Internal base is litres per kilometre (L/km)
  • 1 mile = 1.609344 km · 1 US gal = 3.785411784 L · 1 UK gal = 4.54609 L
  • L/100km is the reciprocal of km/L: L/100km = 100 ÷ (km/L)
  • All math is client-side JavaScript with no server round-trip
How It Works

One Tool for Every Fuel-Economy Convention

Fuel economy is expressed differently around the world — miles per gallon (US and UK), kilometres per litre (Asia and Latin America) and litres per 100 km (most of Europe) — and fuel is priced per litre or per gallon, with the US gallon about 17% smaller than the imperial gallon. The calculator accepts all of these and normalises them, so a driver thinking in 30 US MPG, 36 UK MPG, 12.75 km/L or 7.84 L/100km — all roughly the same car — gets a consistent cost. A round-trip toggle doubles the distance, a people field splits the total, and the result also shows the fuel needed in both US and UK gallons alongside litres.

  • Supports US MPG, UK MPG, km/L and L/100km
  • US gallon (3.785 L) is ~17% smaller than the UK gallon (4.546 L)
  • Round-trip toggle doubles the one-way distance
  • Split-between-people divides the total fuel cost
  • Fuel shown in litres plus US and UK gallons
How It Works

Projecting a Recurring Commute

Commute mode turns a single day’s drive into a budget. Weekly cost = daily cost × days per week; the yearly figure multiplies the weekly cost by 52 weeks, and the monthly figure is the yearly ÷ 12 — the standard approach that avoids the common "× 4 weeks" error, which undercounts annual spend by roughly a month. This makes it easy to see what a daily 40 km round-trip commute really costs over a year, and to compare the running cost of different cars or fuel prices.

  • Weekly = daily × days per week
  • Yearly = weekly × 52; monthly = yearly ÷ 12
  • Avoids the "× 4 weeks" monthly under-count
  • Projects daily, weekly, monthly and yearly fuel spend
  • Useful for comparing cars or commute changes
Limitations

Why Real Fuel Cost Varies

The calculator assumes one steady fuel-economy figure for the whole trip, but actual consumption swings with conditions: stop-start traffic, a heavy load or roof box, air conditioning, hills and headwinds, cold starts, low tyre pressure and aggressive driving can each raise fuel use by 10–30%, and short urban trips are far thirstier than steady motorway cruising. Manufacturer and window-sticker economy figures are typically optimistic, so a realistic estimate uses the mileage a car actually achieves. Fuel prices also vary day to day and station to station, and this tool does not look them up. The output is therefore a well-grounded budgeting estimate rather than a guaranteed amount.

  • Assumes a single steady efficiency for the whole trip
  • Traffic, load, AC, terrain and style can add 10–30%
  • Sticker/manufacturer economy is usually optimistic
  • Fuel prices move and are not looked up
  • An estimator for budgeting, not a guaranteed pump total
Privacy & Security

Privacy and Offline Use

All computation runs in the browser, so the distances, efficiency and prices you enter are never sent to a server, there is no account or tracking, and the page works offline after first load. The calculator is built on a shared, unit-tested fuel-cost engine so its behaviour is consistent and verifiable, and the full result — total cost, fuel needed, cost per km/mile and per person, plus any commute projection — can be copied to the clipboard with one tap.

Fuel cost calculation: in-browser (AnyTool) vs typical online fuel cost calculators
CapabilityAnyToolTypical online fuel cost calculators
ProcessingRuns in your browserOften server-side
Efficiency unitsMPG (US/UK), km/L, L/100kmOften MPG only
Price unitsPer litre or per gallonUsually one only
Round tripOne-tap toggleSometimes
Split between peopleYesRarely
Commute projectionWeekly / monthly / yearlyRarely
Honest limitationStates real-consumption caveatUsually omitted
Works offlineYes (PWA)No
Cost / signupFree, no signupOften ad-heavy or gated

AnyTool computes fuel cost locally and uploads nothing. Comparison as of June 2026.