Rentable square feet (RSF) is the total area a tenant pays rent on in a commercial lease: the usable space inside its suite plus an allocated share of building common areas like lobbies, corridors, restrooms, and mechanical rooms. RSF is always equal to or larger than usable square feet, and it drives the rent bill.
How Is Rentable Square Feet Calculated?
Rentable square feet is calculated by multiplying a tenant's usable square feet by a load factor that adds its pro rata share of common areas. The formula is RSF = Usable Square Feet times Load Factor, where the load factor equals total rentable area divided by total usable area for the floor or building.
The load factor, also called the add-on or common area factor, converts the space a tenant occupies exclusively into the larger number it is billed on. Per PropertyMetrics, load factor equals rentable square feet divided by usable square feet, so a building with 100,000 rentable and 85,000 usable square feet carries a load factor of 1.176, or 17.6% of common area added on top.
Input | Definition |
Usable square feet (USF) | Area inside the tenant's suite it occupies exclusively |
Load factor | Total RSF divided by total USF, a multiplier above 1.0 |
Common areas | Lobbies, corridors, shared restrooms, elevator lobbies, mechanical rooms |
Rentable square feet (RSF) | USF multiplied by the load factor, the number rent is charged on |
Measurement rules set the denominator. Most U.S. markets follow the BOMA standard (ANSI/BOMA Z65.1-2017), which the Building Owners and Managers Association renamed the R/U Ratio to Floor Allocation Ratio. New York City and the surrounding area largely follow the Real Estate Board of New York (REBNY) method, which measures to the exterior face of the window rather than the centerline and produces a larger rentable figure.
Why Rentable Square Feet Matters
Rentable square feet matters because it is the base every rent number is multiplied by, so an inflated RSF quietly raises total rent even when the quoted rate per foot looks competitive. A tenant occupying 8,000 usable feet under a 25% loss factor pays on roughly 10,667 rentable feet, a third more than it can furnish.
Per CommercialCafe, Manhattan loss factors average 20% to 35%, and multi-tenant floors can reach 38% to 39%, so the gap between usable and rentable is material money. For an operator underwriting a lease, confirming how RSF was measured, and under which standard, prevents comparing two buildings on rates that are not measured the same way.
The quotable point for a tenant rep: you sign for rentable square feet, but you can only use usable square feet, and the spread between them is pure carrying cost.
Example
A tenant occupies a suite of 8,000 usable square feet in a multi-tenant office building. The building's load factor is 1.20, reflecting a 20% add-on for common areas. The tenant's rentable square feet is 8,000 times 1.20, which equals 9,600. At an asking rent of $40.00 per rentable square foot, annual rent is 9,600 times $40.00, which equals $384,000.
Step | Calculation | Result |
Usable square feet | Given | 8,000 |
Load factor | Given | 1.20 |
Rentable square feet | 8,000 x 1.20 | 9,600 |
Annual rent | 9,600 x $40.00 | $384,000 |
Effective rent per usable foot | $384,000 / 8,000 | $48.00 |
The rent quoted at $40.00 per rentable foot is effectively $48.00 per usable foot, the number that reflects space the tenant can actually occupy.
Variations and Edge Cases
Rentable square feet is not a fixed convention: the same suite can produce different RSF figures depending on the measurement standard and floor type. A full-floor tenant, a partial-floor tenant, and a REBNY-measured Manhattan space can each show a different rentable number for identical usable area. The table below separates the variants an operator should confirm.
Variant | Treatment |
Full-floor tenant | Lower load factor, sometimes as low as 5%, since fewer shared corridors are allocated |
Multi-tenant floor | Higher load factor, commonly 10% to 15% or more, for shared corridors and restrooms |
BOMA standard | Measures to the centerline of exterior windows; used across most U.S. markets |
REBNY standard | Measures to the exterior face; produces larger RSF, common in New York City |
Re-measurement | Buildings re-measured under a newer standard can shift RSF and rent at renewal |
The common mistake is treating RSF as an objective count. It is a negotiated, standard-dependent figure, and two brokers can quote different RSF for the same physical suite.
Rentable Square Feet vs Usable Square Feet
Rentable square feet is often confused with usable square feet, and the difference is exactly what a tenant pays for but cannot occupy. Usable square feet is the area inside the suite a tenant uses exclusively. Rentable square feet is that usable area plus a pro rata share of building common areas. RSF is always greater than or equal to USF.
The bridge between the two is the load factor. A 10,000 usable-foot suite in a building with a 15% load factor becomes 11,500 rentable square feet. Rent is charged on the 11,500, but only 10,000 can be furnished and occupied. The larger the load factor, the wider the gap.
Frequently Asked Questions
What is the difference between rentable and usable square feet?Usable square feet is the area a tenant occupies exclusively inside its suite. Rentable square feet is that usable area plus a pro rata share of building common areas such as lobbies, corridors, and restrooms. Rent is charged on rentable square feet, which is always equal to or larger than usable square feet.
How do you calculate rentable square feet?Rentable square feet equals usable square feet multiplied by the load factor. The load factor is total rentable area divided by total usable area for the floor or building. For example, 8,000 usable square feet at a load factor of 1.20 equals 9,600 rentable square feet.
Why do I pay rent on more space than I can use?You pay rent on rentable square feet because the figure includes your share of common areas that all tenants use, such as lobbies, corridors, and shared restrooms. The portion above your usable space is captured by the load factor and is the reason effective rent per usable foot exceeds the quoted rate.
Related Terms
Usable Square Feet
Loss Factor
Price Per Square Foot
Common Area Maintenance
Net Effective Rent