This free gas cost calculator works out the fuel cost of any trip or commute in seconds. Enter the distance, your vehicle’s fuel economy, and the price of fuel, and it shows the cost per journey, the fuel you will burn, and the cost per mile or kilometre. It handles both US (MPG, gallons) and metric (L/100km, litres) systems and works in any currency, so you can plan a road trip, price a daily commute, or compare two cars before you drive. No signup required.
Enter the one-way distance, then use the round-trip toggle below for there-and-back.
≈ 7.8 L/100km
For an annual commute, multiply trips per week by weeks (e.g. 5 × 52 = 260).
Trip fuel cost
$11.67
100 mi on 3.33 gallons
Fuel needed
3.33 gallons
Cost per mile
$0.12
Round-trip cost
$23.33
one way $11.67
Fuel is one of the easiest costs to underestimate. Track every fill-up in Auritrack and see exactly what driving costs you each month.
Try Auritrack FreePick the measurement system that matches how you think about fuel. Use Miles / MPG (US style) or Km / L/100km (metric). Your fuel economy figure converts automatically when you switch, so nothing is lost.
Type the one-way distance of your journey in miles or kilometres. For a commute, enter the distance from home to work. You will use the round-trip toggle for the return leg.
Enter your vehicle’s fuel economy (MPG or L/100km) and the current price of fuel per gallon or litre. Check your dashboard trip computer or a recent receipt for accurate figures.
Switch on the round-trip toggle to double the distance for the journey home. To estimate a commute or annual cost, enter how many times you make the trip (for example, 5 days a week over 52 weeks is 260 trips).
Instantly see the fuel cost per trip, the fuel volume needed, the cost per mile or kilometre, and the total across every trip. Change any figure to compare routes, cars, or fuel prices in real time.
Fuel cost comes down to three numbers: how far you drive, how efficiently your car uses fuel, and what fuel costs where you fill up. The maths is simple. First find the fuel used by dividing the distance by your fuel economy, then multiply that volume by the price. A 240-mile drive in a car returning 32 MPG uses 7.5 gallons; at $3.60 a gallon that is $27. The same logic works in metric: a 400 km drive at 7 L/100km burns 28 litres, and at $1.60 a litre that is $44.80. The calculator above keeps every intermediate figure at full precision and only rounds the numbers it shows you, so a long trip does not drift by a few cents.
Fuel cost = (Distance ÷ Fuel economy) × Price per unit
US: gallons = miles ÷ MPG | Metric: litres = km ÷ 100 × L/100km
Two systems dominate the world, and they measure the same thing from opposite directions. Miles per gallon (MPG), used mainly in the United States, tells you how far you travel on a fixed amount of fuel, so a bigger number is better. Litres per 100 kilometres (L/100km), used across most of Europe, Africa, and Asia, tells you how much fuel you burn to cover a fixed distance, so a smaller number is better. Because they are reciprocals, you convert between them with a single constant: divide 235.21 by either figure to get the other. That means 30 MPG equals 7.84 L/100km, and 6 L/100km equals 39.2 MPG. The calculator converts your entry for you when you flip the unit toggle, and it shows the equivalent figure underneath the field so you always have both at a glance. If you are comparing fuel priced in a different currency while travelling, our currency converter helps you translate pump prices into terms you recognise.
Fuel is one of the most controllable costs of running a car, and small changes stack up. Driving style matters most: smooth acceleration, reading the road ahead to avoid hard braking, and easing off the throttle can improve economy by 15 to 30 percent. Speed is a hidden tax, because air resistance climbs steeply above about 60 mph, so cruising at 65 rather than 78 on a motorway can noticeably stretch a tank. Keep tyres inflated to the recommended pressure, since soft tyres increase rolling resistance and quietly cost you a few percent. Strip out the clutter, remove roof boxes and racks when you are not using them, and avoid long idling. On the buying side, filling up mid-week and away from motorway service stations often shaves several cents off every litre or gallon. Try running your real commute through the calculator, then change just the fuel economy figure to see what a more efficient car would save you over a year.
A daily drive that feels cheap per trip becomes a serious line item over a year. Take a 20-mile each-way commute in a 25 MPG car at $3.80 a gallon. Each round trip burns 1.6 gallons and costs about $6.08. That looks trivial until you multiply by roughly 260 working days: over $1,580 a year, before parking, tolls, tyres, or maintenance. Switch to a 40 MPG car and the same commute drops to around $790, an $800 annual saving from fuel alone. This is exactly why the calculator has a “number of trips” field. Enter your trips per week multiplied by working weeks, and it projects the full annual fuel bill so you can weigh it against alternatives like carpooling, remote days, or public transport. When you are deciding whether a particular car fits your budget, feed that annual fuel figure into our car affordability calculator alongside the loan, insurance, and upkeep, and fold the total into a monthly budget plan so nothing sneaks up on you.
The cost-per-mile lens this calculator gives you is also the fairest way to compare a petrol car with an electric one. A petrol car at 30 MPG and $3.50 a gallon costs about 12 cents a mile in fuel. An electric car that travels roughly 3.5 miles per kilowatt hour, charged at home for 15 cents per kWh, costs closer to 4 cents a mile, though public rapid chargers can be several times that and push the figure above petrol. The honest comparison depends on your local electricity and fuel prices, how much you charge at home versus on the road, and how many miles you drive each year. Use the cost-per- mile figure from this tool as your petrol baseline, then work out your electric cost per mile the same way and multiply both by your annual mileage. For most high-mileage drivers charging mainly at home, electric wins on running costs, but the gap narrows if you rely on public charging or drive relatively little. Whichever you choose, tracking what you actually spend at the pump or the plug is the only way to know your true number rather than a sticker estimate.
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Track Fuel Spending
Fuel is easy to underestimate and hard to track. Auritrack logs every fill-up, spots your transport spending trends, and helps you plan around it. Supports all currencies with AI-powered live exchange rates. Free to start.
Disclaimer: This tool is provided for informational and educational purposes only. It does not constitute financial, tax, investment, or legal advice. Results are estimates based on the inputs you provide and may not reflect actual financial outcomes. Always consult a qualified financial professional before making financial decisions.
