Estimate what a trip will cost in fuel and how much fuel you'll burn — from your own distance, fuel economy and price — with a one-way or round-trip toggle, a per-person split and tolls, plus the cost per mile and how far a tank will take you. Works in miles or kilometres, US or imperial gallons, litres, MPG, L/100km or km/L. Enter your own numbers; nothing is looked up and nothing is sent anywhere.
Units — match these to where your figures come from
Left box is the price per US gallon; right box is just the symbol shown in results. No exchange rates.
The trip
Trip type
Optional: share it out
Optional: carbon-dioxide estimate
Petrol/gasoline averages about 2.31, diesel about 2.68 kg of CO₂ per litre — widely-published averages, labelled an estimate.
Per-distance running cost
Uses the fuel economy and price above. Add your own wear-and-tear figure if you want the full running cost rather than fuel alone — there is no built-in rate.
Entered in the currency symbol above. Leave blank for fuel-only cost per mile.
How far on a tank — or fuel for a distance
Enter a tank size to get range; enter a distance to get the fuel it needs. The tank unit follows the price unit (gallons or litres).
An estimate — real fuel use varies with speed, load, terrain, weather and driving style. Use your true economy and current local price for the closest figure.
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Don't know your fuel economy yet?
Measure it with the gas mileage calculator — fill up, note the odometer, drive, refill, and it gives your real MPG, L/100km and km/L. Got your MPG already? You're in the right place to estimate a trip's cost. Comparing heating fuels by energy content instead of a vehicle trip? That's the heating fuel cost comparison calculator.
Work out the fuel cost for a trip
The estimated fuel cost for any journey comes from three numbers you already have or can find: the distance, how much fuel your vehicle uses (its fuel economy or fuel consumption), and the price of fuel. The tool divides distance by economy to get the fuel used, then multiplies by the price — so “how much gas will I use” and “what will this road trip cost” are answered at the same time. Whether you call it petrol or gas, a trip or a journey, the maths is identical; only the labels change. The headline figure is the total fuel cost, with the fuel volume shown underneath so you can sanity-check it against your tank.
fuel used = distance ÷ economy fuel cost = fuel used × price (metric path: litres = distance km × L/100km ÷ 100)
One-way or round trip, split between passengers, plus tolls
The most common slip in a travel fuel-cost estimate is forgetting the return leg, so the calculator has a one-way / round-trip toggle and doubles the distance, fuel and cost when you switch to round trip. If several people are sharing a car, enter how many and it shows the cost per person; add tolls, ferries or parking in the extras box and they roll into the total and the per-person split. Nothing here is looked up — tolls are a figure you type, which keeps the estimate honest and current.
Cost per mile and per km
The running cost per distance is just the price divided by the economy: the fuel cost per mile is the price per gallon divided by miles per gallon, and the petrol cost per km is the price per litre times L/100km divided by 100. The tool surfaces this as cents or dollars (or pence, or any symbol) per mile and per kilometre. If you want the average cost per mile of driving rather than fuel alone, type your own wear-and-tear figure into the extra-cost field; it is added on top, and because there is no baked-in rate the number reflects your actual costs.
How far on a tank — fuel range
Range is tank size times economy, and the inverse — the fuel a given distance needs — is the same relationship the other way around. This fuel-range mode turns “petrol to miles” and “fuel to distance” into a quick planning figure: a 14-gallon tank at 30 MPG is roughly 420 miles between fills. Keep a reserve, because real range drops with speed, a heavy load, hills, cold weather and the simple fact that running a tank to empty is a bad idea.
Miles, kilometres, gallons and litres
Mixing unit systems is where wrong answers creep in, so this calculator keeps every unit explicit and converts through canonical litres and kilometres using exact factors. Distance can be miles or kilometres; fuel economy can be MPG (US), MPG (imperial), L/100km or km/L; and price can be per US gallon, per imperial gallon or per litre. The one trap worth repeating: the imperial gallon (4.54609 litres) is about 20% larger than the US gallon (3.785411784 litres), so a figure quoted in “MPG” means different real economy depending on which gallon it used. Label each box correctly and the litres↔gallons conversion is handled for you.
Exact unit-conversion factors used internally
Quantity
Exact factor
1 US gallon
3.785411784 litres
1 imperial (UK) gallon
4.54609 litres
1 mile
1.609344 kilometres
A worked example
A 300-mile one-way trip, a vehicle that does 25 MPG (US), fuel at $3.50 per US gallon:
Fuel used = 300 ÷ 25 = 12 US gallons (about 45.4 litres).
Fuel cost = 12 × 3.50 = $42.00 one way; round trip is $84.00.
Cost per mile = 3.50 ÷ 25 = 14¢ per mile in fuel.
Split between 3 people, the round trip is $28.00 each.
CO₂ estimate at 2.31 kg/litre ≈ 105 kg one way (an estimate).
The same trip in metric: 482.8 km at 9.4 L/100km is about 45.4 litres — identical fuel, because the conversions are exact.
Terms, in plain English
Term
What it means
Fuel economy / fuel consumption
How far you go per unit of fuel (MPG, km/L) or how much fuel per distance (L/100km). Also called gas mileage.
MPG (US) vs MPG (imperial)
Same idea, different gallon — the imperial gallon is about 20% bigger, so the numbers don't match.
L/100km
Litres to travel 100 km. Lower is better — the inverse of MPG.
Cost per mile / km
Price ÷ economy; the per-distance running cost, fuel only unless you add wear-and-tear.
Range
Tank size × economy — how far you can go before refuelling.
A note for readers across the US, UK and Canada: gas, petrol and gasoline are the same fuel; mileage, fuel economy and fuel consumption describe the same thing; and litre/liter and kilometre/kilometer are just spelling variants. The tool reads them all the same way — pick the units that match your figures and the arithmetic does the rest.
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Frequently asked questions
How do I work out the fuel cost for a trip?
Divide the distance by your fuel economy to get the fuel used, then multiply by the price: fuel used = distance ÷ economy, cost = fuel used × price. For 300 miles at 25 MPG with fuel at 3.50 a gallon, that is 300 ÷ 25 = 12 gallons, and 12 × 3.50 = 42.00 for the trip. In metric the path is distance × consumption ÷ 100 for litres: 500 km at 7.5 L/100km is 37.5 litres, and at 1.60 a litre that is 60.00. This tool does either path for you and converts between units, so you can mix miles with L/100km or kilometres with MPG without doing the conversion by hand.
US gallon or imperial gallon — which one should I use?
It depends on where your figures come from, and getting it wrong is the single biggest source of a wrong answer. A US gallon is 3.785411784 litres and an imperial (UK) gallon is 4.54609 litres, so they are about 20% apart. A car rated 40 MPG on the imperial scale is only about 33 MPG on the US scale for the same real economy. Pick MPG (US) or MPG (imperial) to match where your economy figure came from, and pick the matching price unit — per US gallon, per imperial gallon or per litre. The calculator converts everything to litres internally with the exact factors, so as long as each figure is labelled correctly the result is right.
Does it handle one-way and round trips?
Yes. Forgetting to double the distance for the return leg is a classic mistake, so the tool has a one-way / round-trip toggle and shows both figures. Enter the one-way distance and switch to round trip and it doubles the fuel and the cost; the cost-per-mile and range figures are unaffected because they are per-distance rates. If your outbound and return routes differ, add them together and enter the total as a one-way distance instead.
Can I split the cost between passengers or add tolls?
Yes. Enter the number of people sharing the cost and the tool shows the per-person fuel cost; enter tolls (or parking, ferries, any extra) and it adds them to the total and to the per-person split. Tolls are a figure you type in — nothing is looked up. This is handy for carpools and shared road trips where you want a fair, transparent number rather than a guess.
What about a diesel, an RV or a vehicle that's towing?
There is nothing special to switch on. A diesel, a loaded RV or a vehicle pulling a trailer simply has a different fuel economy, so enter the real, lower economy you actually get under those conditions and the cost follows. If you do not know your true economy, measure it with the gas mileage calculator (fill up, note the odometer, drive, refill, divide distance by fuel added) and bring that number back here. The optional carbon figure lets you switch the emission factor to diesel.
How do I work out the cost per mile or per kilometre?
The fuel cost per mile is the price divided by the economy in the same units: cost per mile = fuel price ÷ miles per gallon, or for metric, price per litre × L/100km ÷ 100. At 3.50 a US gallon and 25 MPG that is 14 cents a mile in fuel alone. If you want the full running cost rather than just fuel, type your own wear-and-tear figure into the extra-cost field and it is added on top — there is no built-in rate, so the number reflects your own costs, not an assumed average.
How far can I drive on a tank?
Range is tank size multiplied by economy: a 14-gallon tank at 30 MPG goes about 420 miles. The range mode does this and the inverse — how much fuel a given distance needs — so you can plan fuel stops. Treat it as a planning estimate and keep a reserve: real range falls with speed, load, terrain, cold weather and a tank you would rather not run to the very bottom.
Is the carbon-dioxide figure accurate, and where does the rate come from?
It is an estimate. The optional CO₂ output multiplies the fuel volume by a widely-published average emission factor — about 2.31 kg of CO₂ per litre of petrol/gasoline and about 2.68 kg per litre of diesel — both of which you can edit. Real emissions vary with fuel blend, vehicle and driving, so the figure is a ballpark for comparing trips, not a certified number. No proprietary or standard table is baked in; it is plain arithmetic on the volume and the factor you choose.
Can I use this to claim mileage reimbursement?
This tool gives you the actual fuel cost and the cost per mile for a trip, which is useful background, but it does not bake in any reimbursement or per-mile rate because those are set by your country, employer or tax authority and change over time. Look up the official published rate that applies to you and compare it against the fuel cost-per-mile shown here. Keeping the rate out means the tool never goes stale and never quotes a figure that does not apply where you are.