Usable vs. Rentable Square Footage

The distinction between usable and rentable square footage is one of the most misunderstood — and costly — details in a commercial lease. Usable square footage is the actual space inside a tenant's suite. Rentable square footage adds a share of the building's common areas — lobbies, corridors, shared restrooms — through the load factor. Because rent and CAM charges are calculated on the rentable figure, a tenant always pays for more square footage than it occupies. A 2,000 usable square foot suite in a building with a 15% load factor becomes 2,300 rentable square feet on the lease. Comparing quoted rents between buildings is meaningless without knowing each one's load factor, since a lower per-square-foot rate on a higher load factor can cost more overall. Healthcare tenants evaluating suites should always ask for both figures before comparing options.

Rent is charged on rentable, not usable, square footage — so the load factor hidden between the two determines your real cost. Comparing suites without it can lead to overpaying for less space.

Two suites both quote $30/sq ft. Suite A offers 2,000 usable sq ft at a 12% load factor (2,240 rentable); Suite B offers 2,000 usable at a 20% load factor (2,400 rentable). Suite B costs $4,800 more per year for the same usable space.