How the math works
Add up everyone's nights. Each person pays their nights divided by the total nights, times the price. For example, three people staying 3, 3 and 1 nights share 7 person-nights, so the one-night guest pays one seventh.
Leftover cents go one each to the first people on the list who stayed at least a night, so the shares match the total exactly.
When an even split is still better
If the house costs the same whether one person stays or ten, some groups prefer to split evenly and let the late arrival chip in for groceries instead. Agree on the method before anyone books, then stick to it.
Put it on the tab with exact amounts
In GroupTab, an expense can be split by exact amounts per person. Turn the calculator's result into a tab and the rental is added with each person's exact share, ready to collect.
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.