How to split gas on a road trip
Quick answer
Work out the fuel cost (miles ÷ mpg × price), then split it by who is in the car. For 600 miles at 28 mpg and $3.50 a gallon, fuel is $75.00. Four equal shares are $18.75 each. If one rider leaves halfway, splitting each 300 mile leg among the people on board is fairer. Tolls, parking and car wear are separate lines.
Key points
- Fuel cost = miles ÷ mpg × price per gallon. For 600 miles at 28 mpg and $3.50 a gallon, that is $75.00.
- Equal per rider works when everyone rides the whole way. When someone leaves partway, split each leg among the people on board.
- A flat per-mile rate is the simplest when the driver rides free. At $0.05 a passenger-mile the passengers cover the fuel in the example.
- Gas does not cover car wear, tolls or parking. Keep them as separate lines so the fuel split stays clean.
On this page
- How do you work out what the gas costs?
- Method 1: equal per rider
- Method 2: by distance, leg by leg
- Method 3: a flat rate per mile
- How do the three compare?
- Should the driver pay a share?
- What does gas not cover?
- How do you log it in EvenOut?
- What should you agree before you leave?
- Frequently asked questions
How do you work out what the gas costs?
Divide the miles by the car’s miles per gallon, then multiply by the price of a gallon. Say a group drives 600 miles round trip in a car that does 28 miles per gallon, with gas at $3.50 a gallon. The car uses 600 ÷ 28 = about 21.4 gallons, and 600 × $3.50 ÷ 28 = $75.00. You can run your own trip through the road trip gas cost calculator.
Everything below splits that $75.00. The riders are four people: Ana drives, Ben and Cam ride the whole way, and Dee gets out at the halfway point, after 300 miles.
Method 1: equal per rider
Divide the fuel by the number of riders: $75.00 ÷ 4 = $18.75 each. It is quick and fine when everyone rides the whole way. Here it is unfair to Dee, who pays the same as Ben and Cam for half the distance.
Method 2: by distance, leg by leg
Split each leg’s fuel among the people who are on board for it. Each 300 mile leg burns $37.50 of fuel. The first leg has four riders, so it is $37.50 ÷ 4 = $9.375 each. The second leg has three, so it is $37.50 ÷ 3 = $12.50 each. Dee pays only for the first leg. Ana, Ben and Cam pay both: $9.375 + $12.50 = $21.875.
Money comes in cents, so two people pay $21.88, one pays $21.87 and Dee pays $9.37. The total is $75.00. The same method handles a rider who joins at a pickup point: they pay only for the legs after it.
Method 3: a flat rate per mile
Agree a rate per passenger-mile before leaving, and the passengers pay it to the driver. Say the rate is $0.05. Ben and Cam each ride 600 miles, which is $30.00, and Dee rides 300, which is $15.00. That is 1,500 passenger-miles × $0.05 = $75.00, so the passengers cover the fuel exactly and Ana pays nothing toward it. It is the least arithmetic on the road, but the rate needs setting from the real fuel cost, or the driver gains or loses.
How do the three compare?
On this trip, Ana pays between $0 and $21.88, depending on the rule, and Dee pays between $9.37 and $18.75. Each column adds to $75.00.
| Rider | Equal | By leg | Flat $0.05 a mile |
|---|---|---|---|
| Ana (drives) | $18.75 | $21.88 | $0.00 |
| Ben | $18.75 | $21.88 | $30.00 |
| Cam | $18.75 | $21.87 | $30.00 |
| Dee (leaves halfway) | $18.75 | $9.37 | $15.00 |
Should the driver pay a share?
Either answer is fine if you agree it before the trip. A driver who pays a share is covered by methods 1 and 2. A driver who rides free leaves the passengers to cover the fuel. With the legs from above, the first leg is $37.50 ÷ 3 = $12.50 each and the second is $37.50 ÷ 2 = $18.75 each. Ben and Cam pay $12.50 + $18.75 = $31.25 each, and Dee pays $12.50. The total is $75.00.
The case for a free ride is that the driver also carries the wear on the car, the insurance and the effort. If the group wants to pay for that, agree a flat amount before leaving and treat it as its own line.
What does gas not cover?
Tolls, parking and wear on the car are separate costs, and mixing them into the fuel figure makes the split hard to check. Tolls go to the people on board at the toll: a $12 bridge toll on the second leg is $12 ÷ 3 = $4.00 each. Parking goes to whoever the car served, usually everyone.
How do you log it in EvenOut?
Make a Trip group, add the riders, and log each fill-up as its own expense.
- Tap “Add expense”, type what was paid at the pump and choose the Fuel category. Set “Paid by” to whoever paid.
- Choose “Split equally”. At the stop after Dee gets out, tap Dee to mark them “Not in”, so the cost splits among three. The first fill-up stays at four.
- For the flat rate, use “Exact amounts” and type $0.00 for Ana, $30.00, $30.00 and $15.00. The pill reads “All assigned” when it adds up to $75.
- Log tolls and parking as their own expenses, with Not in for anyone who was not in the car.
EvenOut splits to the cent and shares any leftover cents, which is how $9.375 becomes whole cents without losing any. A rider who is not on EvenOut can be added with “Add a guest”. At the end of the trip, “Simplify debts” cuts the payments between riders to the fewest needed.
What should you agree before you leave?
Settle four things in one message: whether the driver pays a share, which of the three rules you are using, which costs count beyond fuel, and when you settle up, which is usually once at the end rather than at every stop. The group trip expenses calculator shows who owes whom once everyone has paid something, and how to track group trip expenses covers the rest of the trip’s costs. For a commute with the same riders every week, see how to split carpool costs.
Frequently asked questions
What if the gas price changes during the trip?
Log each fill-up at the price actually paid. The leg by leg method uses the receipts, so no rate has to be guessed. With a flat per-mile rate, add up the receipts at the end. If the fuel came to $84 over 1,500 passenger-miles, the true rate was $0.056, so at $0.05 the driver absorbed $9.
How do I find my car's miles per gallon?
Fill the tank and note the odometer. Drive, fill again, and note how many gallons it took. Miles driven divided by gallons added is your mpg: 336 miles on 12 gallons is 28 mpg. Use the average over a few tanks, not one.
What if we take two cars?
Split each car's fuel among the people riding in that car. Someone who switches cars at a stop counts in each car for the miles they ride there. In EvenOut, tap Not in on the fill-ups of the car someone was not in.
Does this work for an electric car?
Yes, with charging stops in place of fuel stops. Each charging session is a cost paid at a point on the route, so the leg by leg method works the same way. Log each session as its own expense and leave out anyone who was not on board.
Keep reading
- Calculator Road trip gas cost calculator, per person Enter distance, fuel economy, fuel price, tolls and parking to see the trip cost and each rider's share. Works in miles and gallons or km and litres.
- Calculator Group trip expenses calculator: who owes whom Enter what each of up to 6 people paid on a trip and see who is owed and who owes. Balances always cancel out. Includes a 4 person, 5 receipt example.
- Guide How to track group trip expenses as you go A routine for tracking trip expenses as they happen: what counts as shared, logging at the till, an evening check and a charts review at the end.
- Guide How to split carpool costs fairly, with examples Four ways to split carpool costs on one 22-mile commute: equal shares of gas and parking, a per-mile rate, a flat weekly fee and rotating drivers.