Road Trip Fuel Cost Calculator
Estimate what a drive will cost in fuel from the distance, your car’s economy and the local price — with all the awkward units (US & UK mpg, L/100km, km/L, per-litre or per-gallon) handled for you.
- Free, no sign-up
- Works worldwide
- Instant results
All figures come from your inputs — enter your own car’s economy and the local fuel price for an accurate estimate. Real-world consumption varies with terrain, load, traffic and driving style.
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How much will fuel cost for my trip?
Divide the distance by your car’s fuel economy to get the fuel needed, then multiply by the price. For example, 300 miles at 30 US mpg is 10 gallons — at $3.50 a gallon that’s about $35. Enter your own distance, economy and price above (in any units) and the calculator does the conversions, the round trip and the split between passengers.
Methodology: Everything is computed from your inputs — no fuel prices or vehicle data are assumed. Economy is converted to a common litres-per-100km basis (US mpg uses a 3.785 L gallon, UK mpg a 4.546 L gallon), distance to kilometres (1 mile = 1.609344 km), and price to per-litre, then fuel = distance ÷ economy and cost = fuel × price. Round trips double the distance and the split divides the total. Real consumption varies with conditions, so treat it as a close estimate. How we test & calculate.
What a drive actually costs
Fuel is usually the biggest variable cost of a road trip, and it’s easy to under- or over-estimate. The arithmetic is simple — how far you’re going, how thirsty your car is, and what fuel costs — but the units are a minefield, especially if you’re driving abroad and the pump is priced per litre while your car reports miles per gallon. This calculator takes your numbers in whatever form they come and gives you a clean total, a per-person share, and the litres you’ll actually need.
The one formula, and the unit trap
Fuel needed is distance ÷ economy; cost is fuel × price. The trap is mixing systems. A car rated in US mpg isn’t the same as one in UK mpg, because the imperial gallon is about 20% bigger; and most of Europe quotes economy as L/100km (lower is better) rather than a distance-per-fuel figure. The tool keeps all of these straight, converting internally to a single basis, so a 30 US mpg car and an 8 L/100km car are compared correctly. The units converter can translate between them too.
Round trips, passengers and a realistic buffer
Tick round trip and the distance — and the cost — doubles. Add the number of people and you’ll see each person’s share, handy for settling up after a group drive. One honest caveat: the figure is exact for your inputs, but actual consumption depends on terrain, load, speed and driving style, which is why a motorway cruise and a loaded car in hilly traffic can differ by a third. For budgeting, use a slightly pessimistic economy figure or add a 10–15% buffer.
Plan the whole drive
Fuel is one line of a road-trip budget. Pair this with the distance calculator to get the mileage between stops, the driving-abroad checker if you’re crossing borders (side of the road, permits, emergency numbers), and the trip budget calculator to fold fuel in with tolls, parking, food and stays for the full picture.
Frequently Asked Questions
How do I calculate the fuel cost of a trip?
Three numbers: the distance, your car’s fuel economy, and the price of fuel. The amount of fuel you’ll burn is the distance divided by the economy, and the cost is that fuel multiplied by the price. The fiddly part is units — mixing miles with L/100km, or a per-gallon price with a per-litre economy, is where people go wrong. This calculator converts everything consistently so you don’t have to.
What’s the difference between mpg, L/100km and km/L?
They measure the same thing in opposite directions. Miles per gallon (mpg) and kilometres per litre (km/L) are “distance per fuel” — higher is better. Litres per 100 km (L/100km), used across most of Europe, is “fuel per distance” — lower is better. So 8 L/100km is roughly 29 US mpg or 35 UK mpg. The tool accepts whichever your car shows and converts internally, so just pick the matching unit.
Why are US and UK gallons different?
They’re genuinely different volumes: a US gallon is about 3.785 litres while a UK (imperial) gallon is about 4.546 litres — roughly 20% larger. That means a “40 mpg” car means more in the UK than in the US, and a per-gallon fuel price isn’t comparable across the two. The calculator keeps US mpg, UK mpg, US-gallon prices and UK-gallon prices distinct so the maths stays correct.
How accurate is the estimate?
It’s exact for the numbers you give it, but real-world fuel use varies. Hills, headwinds, a heavy load, roof boxes, traffic, air-conditioning and an enthusiastic right foot all push consumption up, while steady highway cruising brings it down. For a safer budget, use a slightly worse economy figure than the manufacturer’s headline, or pad the result by 10–15%.
How do I find my car’s fuel economy?
The quickest way is the trip computer, which usually shows recent average economy. Otherwise, the manufacturer’s figure is on the spec sheet or a quick search of your model, though those tend to be optimistic. The most accurate method is to do it yourself: fill the tank, note the odometer, drive normally, refill, and divide the distance by the fuel added — that gives your real economy for the kind of driving you actually do.
How can I cut the fuel cost?
Beyond the obvious of a more efficient car, the biggest levers are steady speeds (fuel use climbs sharply above about 110 km/h), smooth acceleration and braking, correct tyre pressure, and shedding weight and drag — remove the roof box and empty the boot when you don’t need them. Sharing the drive splits the cost across passengers too, which the calculator can show with the “split between” field.