September 25, 2026 · 6 min read

Rentable vs usable square feet and the loss factor, explained

Most people who look at space in New York eventually notice that the square footage on the listing doesn't match the space they can actually use. That gap is not always a mistake or a trick. It usually comes from the difference between rentable and usable square feet, and the ratio between them, called the loss factor. Once you understand how these numbers relate, you can compare spaces fairly, negotiate better, and avoid paying for more than you expect.

The three numbers you will see

Usable square feet (USF)

Usable square feet is the area you actually occupy and control. It is the space inside your suite where you can put desks, shelving, a reception counter or a conference table. It is usually measured to the inside of the exterior walls and to the middle of walls you share with neighbors.

Rentable square feet (RSF)

Rentable square feet is your usable area plus your share of the building's common areas. Common areas can include:

  • Lobbies and elevator landings
  • Shared corridors on your floor
  • Common restrooms
  • Mechanical and electrical rooms that serve the floor or building
  • Building amenity spaces, depending on the landlord's approach

In NYC commercial real estate, rent is almost always quoted per rentable square foot per year. So if a listing says "5,000 square feet at a given rate per foot," it nearly always means 5,000 RSF, and your usable area will be smaller.

Gross square feet

You may also see gross square feet, especially in building-wide descriptions or on the residential and development side. Gross area generally measures the whole building or floor to the outside of the walls. It is useful for describing a building's size but is less helpful for deciding whether a specific suite fits your needs.

What the loss factor means

The loss factor is the share of rentable space you pay for but cannot use exclusively. The usual formula is:

Loss factor = (RSF minus USF) divided by RSF

A related number is the load factor (sometimes called the add-on factor), which is expressed the other way around:

Load factor = RSF divided by USF

Both describe the same relationship. Landlords, brokers and tenants use either one, so it helps to ask which one someone means when they give you a figure.

A simple illustration

The numbers below are made up to show the math. They are not market data.

Measure Suite A Suite B
Rentable square feet 5,000 5,000
Usable square feet 4,000 3,500
Loss factor 20% 30%
Load factor 1.25 1.43

Both suites are marketed as 5,000 square feet and could carry the same asking rent per foot. Suite A gives you 500 more square feet of usable space for the same money. On a per usable foot basis, Suite B costs noticeably more.

That is the main point of this guide: two spaces with the same listed size and the same price per foot can be very different deals.

Why loss factors vary so much in NYC

Loss factors in Manhattan are often higher than in many other US markets. Several factors drive the differences:

  • Building age and design. Older buildings can have thick walls, large core areas and wide corridors. Newer towers are sometimes designed with more efficient floor plates, but big amenity floors and grand lobbies can push the load back up.
  • Full floor vs multi-tenant floor. A tenant taking a full floor often absorbs the elevator lobby and restrooms as part of their suite, so their usable area can be higher relative to rentable. On a multi-tenant floor, the shared corridor is split among tenants.
  • Measurement method. Landlords do not all measure the same way. New York has a long-standing local measurement practice associated with the real estate industry here, and many landlords also reference national standards such as those published by BOMA. Different methods can produce different rentable figures for the same physical space.
  • Remeasurement over time. Some buildings have been remeasured over the years, and the rentable figure may have grown even though no walls moved.

Because of this, a loss factor that seems high in one building may be normal for its type, and a loss factor that seems low deserves a second look to confirm how it was calculated.

How this affects each type of user

Tenants

Your budget depends on usable space, because that is what your team, equipment and inventory fill. When you compare options, convert everything to an effective cost per usable foot:

Effective rent per USF = Annual rent divided by USF

This one step often changes which space looks like the best deal. Also keep in mind that escalations, operating expense pass-throughs and real estate tax pass-throughs are typically calculated on rentable square feet, so a higher RSF figure costs you in more than one line of the lease.

Buyers and owners

For commercial condos and owned buildings, the rentable number affects the income you can generate, while the usable number affects what tenants will actually accept. A building with an unusually high loss factor may face pushback from tenants and their brokers. Owners should know exactly how their space was measured and be ready to explain it.

In residential sales, square footage in listings and offering plans often reflects a gross or semi-gross measurement and may include a share of walls or other areas. Buyers should not assume the listed figure is the livable interior. Ask for the floor plan and, if the number matters to your decision, consider measuring yourself.

Brokers

Clients rely on you to make apples-to-apples comparisons. Presenting both RSF and USF, along with the loss factor and the measurement standard used, builds trust and speeds up decisions. When a landlord cannot tell you the usable area, that is worth flagging to your client.

Questions to ask before you sign

Ask these on any serious option:

  1. What is the rentable square footage, and what is the usable square footage?
  2. What is the loss factor or load factor for this suite and this floor?
  3. Which measurement standard was used, and when was the space last measured?
  4. Is the loss factor the same across the building, or does it vary by floor?
  5. Can the rentable figure change during the lease if the building is remeasured?
  6. Are operating expenses and tax pass-throughs based on RSF?

It is often reasonable to ask for a clause that fixes the rentable square footage for the term of the lease, so a later remeasurement does not raise your rent. Whether a landlord agrees depends on the building and the market, but it is a common request.

For larger commitments, some tenants hire an architect or measurement professional to verify the numbers. The cost is usually small compared to a few years of paying for space that does not exist.

Lease language on measurement, remeasurement and pass-throughs can have real financial consequences. This guide is general information, not legal or tax advice. Confirm the specifics with a real estate attorney, and talk to an accountant about how occupancy costs affect your finances.

Quick reference

  • Usable is what you occupy.
  • Rentable is usable plus your share of common areas, and it is what rent is usually based on.
  • Loss factor shows how much of the rentable space you cannot use exclusively.
  • Compare spaces on cost per usable foot, not just the asking rent per rentable foot.
  • Ask how the space was measured and whether the figure is fixed for the lease term.

Next steps

There are 24 active listings and 14 active requirements across NYC on Leasemark right now. If you are looking for space, post a requirement with the usable area you need so owners and brokers can respond with options that actually fit. If you have space to fill, list your space and include both rentable and usable figures so tenants can compare it fairly.

To keep exploring:

Keep reading