Work out and split gas money for any drive

A road trip or a shared ride to work starts with a simple question that nobody wants to ask: how much do I owe for gas. The gas cost splitter above answers the second half of it. First work out what the fuel cost, using the formula below, then enter that amount with any tolls and parking, and the calculator shows each person’s exact share.

There is a fairness question too: does the driver pay, and should gas be the only cost? The decision table below covers the common cases.

Work out the fuel cost first

The fuel cost of any drive is:

distance ÷ miles per gallon × price per gallon

Step	Example	Result
Distance	168 miles each way, round trip	336 miles
Gallons used	336 ÷ 28 mpg	12 gallons
Fuel cost	12 × $3.59 a gallon	$43.08

Your car’s dashboard or the manufacturer’s figure gives the miles per gallon. Use the real price you paid at the pump if you know it. Outside the US, use distance in km × litres per 100 km ÷ 100 × price per litre.

How to use the gas cost splitter

1. Add the fuel cost to any tolls and parking for the trip, and type the total as the Bill total.
2. Set Number of people to everyone who shares the cost. Include the driver or not, as you agreed.
3. Leave the tip on No tip.
4. Read Each person pays, and the note about the extra cent.
5. Tap Share result to send the split to the car’s group chat.

Worked example: a weekend road trip

Jess drives Marco and Lee to the lake and back, 336 miles in all. Fuel costs $43.08 as worked out above, and the tolls are $6.50.

Cost	Amount
Fuel	$43.08
Tolls	$6.50
Total	$49.58

Driver included. Enter $49.58 and 3 people. The exact share is $16.5267, so the calculator works in cents: 4,958 ÷ 3 is 1,652 cents with 2 cents left over. Two people pay $16.53 and one pays $16.52. Check: $16.53 + $16.53 + $16.52 = $49.58. Jess already paid for everything, so Marco and Lee each send her $16.53, and her own share is the $16.52 she keeps.

Driver not paying. Enter $49.58 and 2 people: Marco and Lee pay $24.79 each, and $24.79 × 2 = $49.58.

A daily carpool. Three colleagues share an 18 mile drive to work, there and back, five days a week: 18 × 2 × 5 = 180 miles. In a 30 mpg car that is 6 gallons, and at $3.49 a gallon $20.94 a week. Split three ways, each pays $6.98 a week.

Gas only, or gas plus the car

Situation	Fair way to split
Friends on a road trip, one person’s car	Gas and tolls split by everyone, driver included
Driver doing the others a favour	Gas and tolls split by the passengers only
Carpool, everyone takes turns driving	No money changes hands
Carpool, one person always drives	Gas split by everyone, or a per mile rate paid by riders
Rental car	Rental, gas, tolls and parking split by everyone

What about wear and tear? Gas is only part of what a car costs. Tyres, servicing and insurance all add up, and a long trip puts real miles on someone’s car. Some groups agree on a per mile rate instead of gas only. At an agreed 25 cents a mile, the lake trip is 336 × $0.25 = $84.00, plus $6.50 tolls, so $90.50. Split between Marco and Lee, that is $45.25 each. The IRS publishes a business mileage rate each year on irs.gov, which is far higher because it covers the full cost of owning a car, so most friends settle somewhere between gas only and that figure.

When a calculator is not enough

One drive is one calculation. A ski season of weekend trips, a carpool that runs all term, or a road trip where three people filled up at different stations needs a running record. Half Tab keeps every fill-up in a group with who paid it, leaves out anyone who was not in the car for a leg, and shows the fewest payments to settle up at the end. It works offline, which helps on remote roads, and runs on iPhone and iPad in 21 languages.

More calculators and guides

• The travel expense splitter for the whole trip, not just the drive.
• The restaurant bill splitter for the stop on the way.
• The main split bill calculator.
• Our guide on how to split travel expenses.