Quick tip math for any group size
Splitting a bill with tip across a group involves two simple steps that are still easy to get wrong doing quick mental math at the table: calculate the tip on the original bill, add it to get the total, then divide by the number of people.
Tip = Bill × (tip % ÷ 100)
Per person = (Bill + Tip) ÷ number of people
Tipping conventions vary widely
There's no universal "correct" tip percentage — conventions differ significantly by country, and even within a country, by type of service. When traveling or eating somewhere unfamiliar, a quick check of local tipping norms avoids both under-tipping (which can be seen as rude in tip-dependent service cultures) and over-tipping unnecessarily where it isn't expected.