I'm looking to write an equation / function for a lavatory fixture count which will allow calculations below the lowest divisor value.
1 LAV / 40 occupants for the 1st 80 occupants;1 LAV / 80 occupants thereafter.
This equation will not work if I have less than 80 occupants:
=IF(D26>80,(D26-80)/80+80/40), where cell D26 = number of occupants.
= IF( occupants < 80, occupants/40, 1 + occupants/80 )
Since occupants is a single value rather than a list of alternatives, you could also have
= MIN( occupants/40, 1 + occupants/80 )
Either way, to avoid partial fixtures, you will need to round up, giving
= CEILING( IF( occupants < 80, occupants/40, 1 + occupants/80 ), 1 )