I agree house by three, everything else by 5.

Singles should be used to paying more for lodging if they aren't sharing rooms.

Sassafrass your post makes me so sad. I am so sorry you were treated that way. I would never have done that to a friend as I am the exact opposite. I just ask people to give then I kick in the extra so end up paying more than my share. I’ve never shamed anyone if they needed to be covered.

That being said, I would divide it all by 5. I have never had a problem but know people who will only travel with me because I am “fair” when it comes to money. To save money, I once got a place that wasn’t a hotel but more like extended stay. I had reserved a 3 bedroom for 3 people but got only 2 bedrooms so 2 had to share. Dividing by 3 still wasn’t an issue because because who would have had to pay more if only dividing by 2? I could not make that decision so we split it by 3. There were times on that trip when 2 paid for 3 or one spotted the other with money. No one was keeping track because we tried to be as fair as possible on other things.

Five people are sharing the house. Divide the cost of the house by five.

Sassy27,
You are so kind. My very small town, mid-western background was pretty limited and going out to eat was not something we did, so it was all just a big surprise. It was actually a good life lesson, which taught me to be sure then and especially later when DH and I had plenty that we were generous with people, hopefully never letting them feel uncomfortable about it.
I am old now and mostly go out with people I really care about, so much so that I just want their company, not their money, so prefer to pick up the tab if I can.

If the 3 bedrooms are identical, then divide by 3.

Everything else is per person.