The direct answer
Usable square feet measure the space a tenant can generally occupy for its exclusive use, while rentable square feet can include an allocated share of common areas. The load factor expresses the relationship between rentable and usable area and affects quoted rent comparisons.
Use the same measurement standard
Area definitions can vary by building type, lease and measurement standard. Compare quoted rents only after confirming whether the rate is applied to usable or rentable area.
To apply the approach to an editable scenario, use the Commercial Rent Calculator. For the neighboring question, explore NNN Lease Calculator.
Understand the load factor
A higher load factor means more common-area allocation is included in rentable area relative to usable area. That can increase total rent even if the quoted rent per rentable square foot is unchanged.
Compare total occupancy economics
Two spaces with the same usable area can have different rentable area, common-area allocation and effective occupancy cost.
Worked example
If a suite has 10,000 usable square feet and a 15% load factor, it may be billed on about 11,500 rentable square feet under a simplified calculation. At $30 per rentable square foot, annual base rent would be $345,000.
Common mistakes and limitations
Do not compare one property’s $/usable-square-foot quote directly with another property’s $/rentable-square-foot quote.
Lease definitions of rentable area, CAM, exclusions, caps and reconciliations vary by contract.
Frequently asked questions
Is rentable square footage usually larger than usable square footage?
Often yes in multi-tenant buildings because rentable area can include a share of common space.
Is load factor standardized across every property?
No. Measurement conventions and building layouts can differ.
Sources and further reading
The article’s examples are illustrative arithmetic. The references below provide context for operating, valuation or transaction concepts; they do not endorse the assumptions or the calculator.
- Office of the Comptroller of the Currency — Comptroller's Handbook — Commercial Real Estate LendingNOI, direct capitalization, cap-rate valuation and DCF concepts for commercial real estate.
Read our editorial policy for the scope of these educational methods.