When you lease commercial space, the square footage on the lease is usually larger than the space you can actually use. The difference comes from shared areas like lobbies, hallways, and restrooms. Understanding rentable square feet, usable square feet, and the load factor helps you compare spaces fairly and avoid paying for more than you expected.
Usable Square Feet
Usable square feet (USF) is the space inside your suite that only your business occupies. It includes your offices, open work areas, conference rooms, and any private restrooms or storage inside your walls.
Rentable Square Feet
Rentable square feet (RSF) is your usable space plus your share of the building’s common areas, such as the lobby, corridors, shared restrooms, mechanical rooms, and elevator lobbies. Rent is almost always quoted on rentable square feet.
The Load Factor
The load factor, sometimes called the add-on factor or common area factor, shows how much common area is added to your usable space. It is calculated like this:
Load factor = Rentable square feet ÷ Usable square feet
A load factor of 1.15 means you pay for 15% more space than you occupy. Single-tenant buildings may have no load factor at all, while multi-story office buildings often run between 1.10 and 1.20.
A Worked Example
Here is an illustrative comparison of two Sarasota office suites with the same usable space but different load factors.
Item | Suite A | Suite B |
|---|---|---|
Usable square feet | 3,000 | 3,000 |
Load factor | 1.10 | 1.20 |
Rentable square feet | 3,300 | 3,600 |
Quoted rent per RSF | $28.00 | $26.00 |
Annual rent | $92,400 | $93,600 |
Effective rent per USF | $30.80 | $31.20 |
Suite B has the lower quoted rent, but it costs more for the same usable space because of its higher load factor.
Quoted vs Effective Rent
This chart compares each suite’s quoted rent with what it costs per square foot you actually use.
Rent | Per sq ft | Chart |
|---|---|---|
Suite A quoted (RSF) | $28.00 | ██████████████ |
Suite A effective (USF) | $30.80 | ███████████████ |
Suite B quoted (RSF) | $26.00 | █████████████ |
Suite B effective (USF) | $31.20 | ████████████████ |
How to Compare Spaces Fairly
Ask for both numbers. Get the usable and rentable square feet for every space you consider.
Calculate the load factor for each building.
Convert rent to cost per usable square foot so the comparison is apples to apples.
Add the pass-through costs. A NNN lease adds taxes, insurance, and CAM on top of base rent.
Check the measurement. Ask which standard was used and whether the space has been measured recently.
Frequently Asked Questions
Is the load factor negotiable?
The load factor itself comes from the building’s design, but the rent, concessions, and how the space is measured can be negotiated. Some tenants negotiate a cap on the load factor or the right to have the space remeasured.
Who measures commercial space?
Most landlords use an architect or measurement firm that follows a BOMA standard, published by the Building Owners and Managers Association. Different standards can produce different numbers, so it is worth asking which one was used.
Do CAM charges use rentable square feet?
Usually, yes. A tenant’s share of CAM charges is typically its rentable square feet divided by the building’s total rentable area.
If you are comparing spaces and want help reading the numbers, get tenant representation or call Eric Barnes at 941-207-9707.
For property owners
Get tenant representation
About the author: Eric Barnes
Eric Barnes | Commercial Advisor | 941-207-9707
Michael Saunders & Company | MSC Commercial | Sarasota, Florida
Florida License SL3600406 | GRI | RSPS
More about Eric Barnes