How to calculate gas money
First work out the gallons: miles divided by MPG. Multiply by the price per gallon to get the cost of the gas, add any tolls and parking, then divide by the number of people paying.
For example, a 300-mile drive at 25 MPG uses 12 gallons, so at $3.50 a gallon the gas costs $42, or $10.50 each for four people.
Should the driver pay for gas?
Groups do it both ways. Many leave the driver out, since they bring the car and do the driving, so only the passengers split the gas. Others split it evenly, driver included, especially when people take turns driving.
Either is fair if it's agreed before you leave. Say it in the group chat when you plan the drive, not at the pump.
Count the whole drive
For a round trip, count both ways, plus any side trips. Use the car's own MPG and the price you actually paid, and add tolls and parking so the driver isn't covering them alone.
Once you're back, the gas receipts are the real number. If you have them, add each fill-up to the tab as its own expense and split it the same way.
Collect it with one link
Whoever paid for the gas turns the result into a tab and sends the group the link. The gas goes in paid by them, split among everyone, or among everyone but the driver if you ticked the box.
GroupTab keeps everyone's Venmo and Cash App in the tab, so paying is one tap with the amount already filled in, and both sides confirm when it arrives.