Size a shared family cloud plan by combining the storage each member needs plus a growth allowance.
Rated capacity is a ceiling, not a design point, so it is derated by the headroom percentage before dividing. The result is rounded up because you cannot deploy a fraction of a plan seat. Sizing to rated capacity leaves nothing for peaks or failures; the spare-capacity line shows whether the rounded-up count actually buys useful family storage.
Family Cloud Storage
Units = ⌈demand ÷ (capacity per unit × (1 − headroom))⌉
Units = ⌈demand ÷ (capacity per unit × (1 − headroom))⌉ Rated capacity is a ceiling, not a design point, so it is derated by the headroom percentage before dividing. The result is rounded up because you cannot deploy a fraction of a plan seat.
Sizing to rated capacity leaves nothing for peaks or failures; the spare-capacity line shows whether the rounded-up count actually buys useful family storage.
This calculator takes 3 inputs: Total data across the family, Storage per plan seat, Headroom reserved for peaks. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.