Understanding Usable vs. Rentable Square Footage in Commercial Real Estate

marketing08413
Sep 17
2 min read

When leasing commercial space, one of the most common points of confusion is the difference between Usable Square Footage (USF) and Rentable Square Footage (RSF). These two measurements directly impact how much space you actually get—and how much rent you pay. Here’s a simple breakdown.

What Is Usable Square Footage (USF)?

Definition: Usable Square Footage is the space a tenant can physically occupy and use for their business operations.

Includes:

Offices, conference rooms, storage areas, and any rooms inside the tenant’s suite.

Does not include:

Shared/common areas such as hallways, restrooms (outside the suite), lobbies, stairwells, and elevators.

Why it matters: USF is what your employees and clients actually use on a day-to-day basis.

What Is Rentable Square Footage (RSF)?

Definition: Rentable Square Footage is the amount of space a tenant pays rent on. It includes your usable space plus your proportionate share of the building’s common areas.

Example: If you lease 1,000 USF in a building where shared areas make up 15% of the building, your RSF would be 1,150 SF (your usable space plus 15% of the common areas).

Why it matters: Landlords base rent on RSF, not USF, since tenants benefit from common areas even though they don’t exclusively occupy them.

The Load Factor (Common Area Factor)

The difference between USF and RSF is captured in what’s called the load factor (or common area factor).

Formula: RSF ÷ USF
Typical range: 10%–20%, depending on the building’s design.
Impact: A higher load factor means you’re paying for a greater share of common areas.

Quick Recap

USF = What you use.
RSF = What you pay for.
Load Factor = The percentage that bridges the two.

Final Thoughts

When reviewing a lease, always confirm whether the square footage quoted is usable or rentable. Two office suites of the same size could have very different rent costs depending on the building’s load factor. Understanding these terms ensures you know exactly how much space you’re getting—and what you’re paying for.