How do you calculate fuel cost for a trip?

Find fuel used, then multiply by price. Metric: litres = (distance km ÷ 100) × L/100 km. US customary: gallons = miles ÷ MPG. Cost equals that volume times price per litre or gallon.

What is the difference between L/100 km and MPG?

L/100 km measures litres burned per 100 kilometres—lower is more efficient. MPG measures miles per gallon—higher is more efficient. They move in opposite directions, so never mix them without converting.

Does the estimate include tolls, parking, or wear?

No. It is fuel only. Add highway tolls, city parking, hotel overnight charges, and a maintenance reserve separately if you need a full trip wallet number.

Are US gallons and UK imperial gallons the same?

No. This calculator’s MPG path uses US gallons (about 3.785 L). UK imperial gallons are larger; UK mpg figures are not interchangeable without conversion.

Why is my real tank cost higher than the estimate?

Cold starts, stop-and-go traffic, hills, headwinds, heavy loads, underinflated tires, and speeding all raise consumption above the steady figure you entered. Brochure ratings are often optimistic for mixed driving.

Can I budget a whole month of commuting?

Compute one round-trip day’s cost, then multiply by commuting days. Keep a buffer for detours and seasonal A/C or heater loads that change efficiency.

Should I use highway or city efficiency?

Match the rating to the trip. Pure interstate runs lean toward highway numbers; errands and urban cores need city or mixed figures to avoid under-budgeting.

How do diesel and petrol prices fit in?

Enter whichever fuel your vehicle burns at the price you will actually pay. The math is identical; only efficiency and price inputs change.

Can I compare EV energy cost with this tool?

Not directly—the interface is built around liquid fuel units. For EVs, multiply kWh used by electricity price in a separate estimate, then compare dollars or euros per trip.

What distance should I enter for a round trip?

Enter the full distance you will drive, outbound plus return, unless you intentionally want a one-way cost. Forgetting the return leg is a common under-estimate.

Do elevation and altitude matter?

They can. Continuous climbing and thin air at altitude often worsen economy. Inflate L/100 km (or cut MPG) when your route is notably mountainous.

Are trip inputs stored on a server?

Calculations run locally in the browser from what you type. You can plan routes privately; still use an offline map or your own notes if you prefer not to type sensitive address details into any web form.

Fuel Cost Calculator

Use this fuel cost calculator when you need a quick estimate of how much petrol or gasoline a trip will burn through your wallet. Enter distance, your vehicle’s efficiency in L/100 km or MPG, and the price per litre or gallon; the tool returns fuel volume and total cost, plus a cost-per-distance reading for comparing cars or routes. It is ideal for weekend drives, holiday planning, and commuting budgets. It does not quote live pump prices, include tolls or parking, or adjust automatically for hills, traffic, roof boxes, or aggressive driving—real consumption often runs higher than the sticker figure you typed.

Trip distance

Distance unitFuel economy

Litres per 100 kmEconomy unitFuel price

Price unit

Total trip cost

$49.50

Fuel needed (Litres)

30.00 L

Cost per km

$0.12

Quick answer

Trip fuel cost equals fuel used multiplied by price per unit. For metric: litres = (distance km ÷ 100) × L/100 km, then cost = litres × price per litre. For imperial: gallons = miles ÷ MPG, then cost = gallons × price per gallon.

Informational only; verify critical results independently.

How to use

Measure or map the full one-way or round-trip distance you will drive, then enter that total and select kilometres or miles so units stay consistent end to end.
Enter your vehicle’s typical fuel efficiency as L/100 km (metric) or miles per US gallon (imperial), preferring recent onboard-computer averages over optimistic brochure ratings when you have them.
Look up a realistic local pump price and enter it with the matching unit—price per litre with L/100 km, or price per US gallon with MPG—to avoid mixed-unit mistakes.
Read total fuel needed and total trip cost first; those two numbers answer most road-trip budgeting questions in one glance.
Check cost per kilometre or mile when comparing two cars on the same route, because total cost alone can hide which vehicle is leaner.
Copy any result card if you are building a travel spreadsheet, then change distance or price to model alternate stops or a longer scenic loop.
For a daily commute, enter the round-trip distance once and multiply the daily cost by workdays per month outside the tool for a payroll-week budget.
When comparing hybrid versus older petrol cars, hold distance and price fixed and only change efficiency so the savings you see are attributable to economy alone.
If you will tow a trailer or carry a roof box, inflate the efficiency figure (higher L/100 km or lower MPG) by a personal safety margin before trusting the estimate.
Recalculate near departure day with updated pump prices; a ten-cent swing per litre on a long holiday can add meaningful currency to the tank.

Examples

400 km at 7.5 L/100 km with fuel at $1.65/L → 30 L used and about $49.50 total (~$0.124/km).
300 miles at 30 MPG with gas at $3.50/gal → 10 gallons and $35.00 total (~$0.117/mile).
Daily 50 km commute at 6 L/100 km and $1.80/L → 3 L and about $5.40 per day; twenty workdays ≈ $108/month in fuel alone.
Weekend 200-mile drive at 28 MPG and $3.20/gal → about 7.14 gal and $22.86 before any return-leg premium pricing.
Same 500 km trip: car A at 5.5 L/100 km versus car B at 8.5 L/100 km with diesel/petrol at $1.70/L → roughly $46.75 versus $72.25—about $25.50 difference.
Rental return: 150 km, 9 L/100 km, diesel at €1.55/L → 13.5 L and about €20.93; useful when deciding whether to refill off-airport.
Cross-country sketch: 1,200 miles at 26 MPG and $3.75/gal → about 46.2 gal and $173 trip fuel for that leg.
City hop: 85 km at 10 L/100 km (congested) and $1.90/L → 8.5 L and $16.15—shows how traffic-heavy ratings inflate cost.
Highway cruise: 85 km at 5.8 L/100 km and $1.90/L → about 4.9 L and $9.35 on the same corridor with steadier speeds.
Two fills on a holiday: 640 km total at 7 L/100 km and £1.45/L → 44.8 L and about £65 before snacks and tolls.

FAQ

How do you calculate fuel cost for a trip?: Find fuel used, then multiply by price. Metric: litres = (distance km ÷ 100) × L/100 km. US customary: gallons = miles ÷ MPG. Cost equals that volume times price per litre or gallon.
What is the difference between L/100 km and MPG?: L/100 km measures litres burned per 100 kilometres—lower is more efficient. MPG measures miles per gallon—higher is more efficient. They move in opposite directions, so never mix them without converting.
Does the estimate include tolls, parking, or wear?: No. It is fuel only. Add highway tolls, city parking, hotel overnight charges, and a maintenance reserve separately if you need a full trip wallet number.
Are US gallons and UK imperial gallons the same?: No. This calculator’s MPG path uses US gallons (about 3.785 L). UK imperial gallons are larger; UK mpg figures are not interchangeable without conversion.
Why is my real tank cost higher than the estimate?: Cold starts, stop-and-go traffic, hills, headwinds, heavy loads, underinflated tires, and speeding all raise consumption above the steady figure you entered. Brochure ratings are often optimistic for mixed driving.
Can I budget a whole month of commuting?: Compute one round-trip day’s cost, then multiply by commuting days. Keep a buffer for detours and seasonal A/C or heater loads that change efficiency.
Should I use highway or city efficiency?: Match the rating to the trip. Pure interstate runs lean toward highway numbers; errands and urban cores need city or mixed figures to avoid under-budgeting.
How do diesel and petrol prices fit in?: Enter whichever fuel your vehicle burns at the price you will actually pay. The math is identical; only efficiency and price inputs change.
Can I compare EV energy cost with this tool?: Not directly—the interface is built around liquid fuel units. For EVs, multiply kWh used by electricity price in a separate estimate, then compare dollars or euros per trip.
What distance should I enter for a round trip?: Enter the full distance you will drive, outbound plus return, unless you intentionally want a one-way cost. Forgetting the return leg is a common under-estimate.
Do elevation and altitude matter?: They can. Continuous climbing and thin air at altitude often worsen economy. Inflate L/100 km (or cut MPG) when your route is notably mountainous.
Are trip inputs stored on a server?: Calculations run locally in the browser from what you type. You can plan routes privately; still use an offline map or your own notes if you prefer not to type sensitive address details into any web form.

Formula / Method

Metric: litres = (distance_km / 100) × L_per_100_km; cost = litres × price_per_litre. Imperial: gallons = miles / MPG; cost = gallons × price_per_gallon. Cost per distance = total cost ÷ distance. Keep distance, efficiency, and price units on the same measurement system for each scenario.

Assumptions & Limitations

Assumes constant efficiency and a single fuel price for the whole distance. It ignores elevation profiles, traffic queues, cold-start idling, and split fills at different stations or currencies. Output is a planning estimate only—not a pump receipt, live price feed, or fleet-accounting audit.

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Last updated: 2026-07-13

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