01
These are assumptions, not industry statistics.
The defaults sit at the conservative end of what UK operators tell us. They are a starting point for a conversation with your finance lead, not a benchmark you can cite. Change them to match your business.
02
It deliberately leaves out the expensive part.
Lost covers from understaffed shifts, the service dip a stretched rota causes, damaged reviews, and the contagion effect where one exit triggers the next — all real, none of them modelled here, because none can be estimated honestly without your data.
03
The result is therefore a floor.
Whatever figure you get is the least turnover is costing you, not the most. That is the right way round for a number you intend to take to a board.