Our house has 1 bathroom (kids ) and 1 (ensuite)
We have 4 towels each, 2 hand towels each, 1 bath mat each bathroom.
Two sets of flannelette sheets for each bed for winter.
3 sets of cotton sheet sets for summer for each bed.
3 Duvet covers for our bed, 1 each for the kids.
Tea Towels x 7
Spare blankets x 2
Spare Duvets x 2
Spare pillows x 2
Spare towels x 4

Our linen cupboard is big, so we also store photo's in it, it also has my wedding dress in the box after dry cleaning. We keep, wrapping paper and other bibs and bods in it as well. It's a very generous linen cupboard.

ETA: We are a five person household