Gas money calculator
To split gas money, work out the gas cost of the trip, then divide it. A 600-mile round trip at 30 MPG and $3.995 a gallon uses $79.90 in gas: about $19.98 each for 4 people, or less for someone who rode only part of the way.
On this page (6 sections)
How to use the calculator
- Trip. Enter the miles, the car’s MPG, and the gas price. If you already know what the gas cost (from the receipts), you can enter the dollar total instead.
- People. Add everyone who shares the cost. Decide first whether the driver pays a share.
- Method. Pick even split if everyone rode the whole way. Pick by miles and enter each person’s miles if some rode less.
The result shows each person’s share. When the total doesn’t divide evenly to the cent, some shares are one cent more than others, so the shares always add up to the total.
Even split: the formula
Each share = total gas cost ÷ number of people.
Gas cost = miles ÷ MPG × price per gallon. For the example: 600 ÷ 30 = 20 gallons, and 20 × $3.995 = $79.90. Split among 4 people (the driver and 3 friends), that is $19.975, or about $19.98 each. If the driver does not pay a share, the 3 riders pay $26.63 each.
Split by miles: the formula
When people ride different distances, split by “rider-miles”: one rider-mile is one person in the car for one mile.
- Add up everyone’s miles. This is the total rider-miles.
- Each share = total gas cost × (that person’s miles ÷ total rider-miles).
This way, a mile driven with 4 people in the car costs each of them a quarter of that mile’s gas, and a mile driven with 2 people costs each of them half.
Example: a road trip where one friend rides half the way
The driver, Ana, and Ben ride the full 600 miles. Cam rides only one way, 300 miles, and flies home.
| Person | Miles in the car | Share of rider-miles | Pays |
|---|---|---|---|
| Driver | 600 | 600 ÷ 2,100 | $22.83 |
| Ana | 600 | 600 ÷ 2,100 | $22.83 |
| Ben | 600 | 600 ÷ 2,100 | $22.83 |
| Cam | 300 | 300 ÷ 2,100 | $11.41 |
| Total | 2,100 | $79.90 |
An even split would have charged Cam $19.98 for half the trip. Split by miles, Cam pays $11.41 and the others pay a little more.
For tips on picking a method with friends, carpools, and one-off rides, read how to split gas money.
Common mistakes
- Using the EPA MPG for an old or loaded car. A full car with luggage often gets less than its rating. If you know the car’s real MPG, use it. The MPG calculator finds it from one fill-up.
- Splitting the receipt for the last fill-up only. The car may have started the trip with a full tank that someone else paid for. Split by the miles of the trip, not by what was pumped on the way.
- Forgetting tolls and parking. Add them as a separate line and split them the same way, or evenly. The gas trip calculator has a field for tolls.
- Not agreeing first. Pick the method before the trip. It is easier than debating it at the end.
FAQ
Should the driver pay a share of the gas?
Either way is common. On a shared trip where everyone wanted to go, the driver usually pays a share like everyone else. When the driver is doing someone a favor, riders often cover all of the gas. Agree on it before you leave.
How do I split gas when people ride different distances?
Use the by-miles method: add up each person’s miles in the car, then give each person a share of the gas cost equal to their miles divided by the total. In the example above, Cam rode 300 of 2,100 rider-miles and pays $11.41 of $79.90.
Should gas money cover more than gas?
Gas is the usual minimum. Some groups add tolls, parking, or a little for the driver’s wear and tear, since tires, oil, and repairs also cost money per mile. One benchmark for the full cost of driving is the IRS mileage rate, which is set for business driving and is much higher than gas alone.