Road Trip Gas Calculator: Fuel, Tolls and Cost Per Person

Road trip gas cost: fuel, tolls and each passenger's share

Cost = miles ÷ MPG × price per gallon, plus tolls (counted twice for a round trip) and parking, divided by the number of people (or litres per 100 km in metric mode). For a 350-mile trip each way at 28 MPG and $4.33/gal with $12.50 of tolls each way, the round trip costs $133.25, or $44.42 each for three people.

Calculation

• Total distance = distance × 2 when the round-trip option is ticked.
• Imperial mode (default, designed for the US): gallons = miles ÷ MPG; metric mode: litres = km ÷ 100 × L/100 km.
• Tolls: the amount entered is for one direction. It is doubled when the round-trip option is ticked, and the doubled total is shown under the field. Parking is entered separately and counted once.
• Optional wear and tear, off by default: total distance × rate per mile or per km.
• Total cost = fuel + tolls + parking + any wear; cost per mile or km = total cost ÷ total distance.
• Share per person = total cost ÷ number of people (1 to 10), driver included. With the "Driver rides free" option, the total is divided among the passengers only (number of people − 1).
• CO₂ = gallons × 8.887 kg or litres × 2.348 kg (the same gasoline factor per litre), so both modes give the same result.

Example

Three friends drive 350 miles each way, 700 miles in total, in a 28 MPG car with gas at $4.33 per gallon. They enter $12.50 of tolls for one direction, which the tool doubles to $25, and $10 of parking. The 25 gallons cost $108.25 and the total is $143.25: $47.75 each, for about 222 kg of CO₂. If the driver rides free, each of the two passengers pays $71.63. With wear and tear at $0.10 per mile, $70 is added over 700 miles: the total becomes $213.25, or $71.08 each, or $106.63 per passenger if the driver rides free. In metric mode, 400 km each way at 7.5 L/100 km and €2.00 per litre, with €15 of tolls per direction and no parking, come to €150, or €50 each.

Tolls in Spain and France: where to find the rate

The tool does not plot a route or look up any rate: you type in the one-way toll as shown by the motorway operator or your route planner. In Spain, the Ministry of Transport revises state motorway tolls every year: in 2026 they rose by 3.64% to 4.68% on concession motorways and by 2% on those run by SEITT, which are free from midnight to 6 a.m. (Spanish Ministry of Transport press release, 12/30/2025); the ministry also publishes rate tables by motorway. In France, the portal of the motorway companies (ASFA) gives the toll price for a route (autoroutes.fr, routes and prices). If the return leg takes a different route, enter the average of the two directions. Pages checked on 10/22/2026.

Limits

• The pre-filled fuel price is only a starting point: enter the pump price, which changes weekly and from one station to the next. In metric mode, the €1.85/L default is indicative and unverified.
• The starting wear rate, 0.10 per mile in imperial mode and 0.06 per km in metric mode (the same rate converted and rounded), is indicative: replace it with your own estimate for tires, brakes and maintenance.
• The CO₂ factor is for gasoline, even for diesel cars; insurance is not included.
• In France, carpooling must remain cost-sharing with no profit for the driver (Transport Code, art. L3132-1, cited without online check): the tool only calculates costs.

Sources and dates: imperial default price = US regular gasoline average, $4.331/gal for the week of 10/12/2026 (EIA, Gasoline and Diesel Fuel Update); 8,887 g of CO₂ per gallon of gasoline (EPA, updated 08/04/2026); in metric mode, that factor divided by 3.785 L per gallon, i.e. 2.348 kg per litre. Checked on 10/14/2026.

Frequently Asked Questions

How do I calculate gas cost for a road trip?

Divide the total miles by your car's MPG and multiply by the price per gallon. For 700 miles at 28 MPG and $4.33/gal, you need 25 gallons, or $108.25.

Are tolls doubled for a round trip?

Yes: enter the toll for one direction and the tool doubles it when the round-trip option is ticked, showing the total under the field. Parking is entered separately and counted once.

How should passengers split gas money?

The tool divides the total cost (fuel, tolls, parking and any wear) by the number of people, driver included. A $133.25 trip shared by three comes to $44.42 each; if the driver rides free, each of the two passengers pays $66.63.

How much CO₂ does a road trip emit?

The tool uses the EPA figure of 8,887 grams of CO₂ per gallon of gasoline. Burning 25 gallons releases about 222 kg of CO₂.

How does this fuel cost calculator handle tolls and parking?

Tolls are entered for one direction and doubled for a round trip; parking is added once. For 700 miles at 28 MPG and $4.33 per gallon, with $12.50 of tolls each way and $10 of parking: $108.25 + $25 + $10 = $143.25.

How do you split carpool costs, wear and tear included?

Tick the wear and tear option and enter a rate per mile, 0.10 by default: over 700 miles it adds $70. A $143.25 trip then comes to $213.25, which is $71.08 each for three people, or $106.63 per passenger if the driver rides free.

Does the calculator look up the tolls for my route?

No: the tool does not plot a route. Type in the one-way toll yourself; it is doubled when the round-trip box is ticked. Use the toll operator's rate table or your route planner. In Spain, the Ministry of Transport publishes state motorway rates each year, and in France the motorway companies' portal gives the toll for a route.

Is this tool really free?

Yes, all tools on Kristools are 100% free and accessible without registration.

Is my data protected?

Yes. All processing is performed directly and securely inside your browser. No personal data is sent to our servers.