Unit growth is not enough
A 10% increase in units does not always mean 10% more storage space. Case pack changes, palletization, SKU proliferation, product dimensions and safety stock policies can all alter the relationship.
Forecast by storage family
Grouping inventory into pallet, shelf, bin, hanging, floor-stack or other storage families can produce a more useful forecast than one warehouse-wide average.
Use peak on-hand inventory
Capacity needs are driven by the maximum expected inventory on hand, not annual throughput. A fast-moving operation can ship enormous volume through a modest footprint if inventory turns quickly.
Track forecast error
Compare predicted and actual peak inventory after each season or planning cycle. Improving the forecast process can be cheaper than repeatedly buying capacity to compensate for uncertainty.
Practical questions
Should I use one utilization percentage for every warehouse?
No. Inventory profile, storage system, seasonality, staging demand, handling equipment and workflow can make the same percentage perform very differently in two facilities.
Can this guide be used to approve a rack or building change?
No. It is a planning resource. Structural, fire, building, accessibility and workplace-safety requirements must be established for the actual facility by the appropriate qualified parties and authorities.