Understanding Rentable vs. Leasable Square Feet

If you've ever looked at an office listing and wondered why the square footage you're paying for doesn't exactly match the space you'll occupy, you're not alone. Two of the most common terms you'll hear in commercial real estate are rentable square feet (RSF) and leasable square feet, and while they sound similar, they mean different things.

What is Rentable Square Feet (RSF)?

Rentable square feet is the amount of space you actually pay rent on. It includes:

• Your private office space, workstations, conference rooms, break rooms, and other areas your company uses. This is also referred to as Usable Square Feet (USF).

• Plus, your share of the building's common areas, such as the lobby, hallways, restrooms, elevator lobbies, and shared amenities.

Another way to think of it is like living in a condominium. You own your individual unit, but you also help pay for the lobby, hallways, and amenities that everyone shares.

Here's a simple example:

Let's say your office itself measures 5,000 square feet. If the building has a 15% load factor (the percentage of common areas shared among tenants), your rentable square footage becomes 5,750 square feet.
(5,000 x .15) +5,000 = 5,750 square feet)

If the rental rate is $30 per rentable square foot, your annual rent would be:

5,750 RSF x $30 = $172,500 per year.

What is Leasable Square Feet?

Leasable square feet doesn't describe how space is measured. Instead, it describes space that's currently available to rent.

For example, an office building contains 100,000 rentable square feet. If 80,000 square feet is already leased, the remaining 20,000 square feet is considered leasable because it's available for a new tenant.

When you see a listing that says:

"15,000 square feet available for lease,"

It's simply telling you that 15,000 square feet is currently on the market. In most office buildings, that number is typically expressed as rentable square feet (unless noted otherwise).

The takeaway?

Rentable square feet tells you what you're paying for, while leasable square feet tells you what's available. Knowing the difference can help you compare office spaces more confidently, avoid surprises when reviewing lease terms, and better understand how commercial real estate listings are presented. The more familiar you are with these terms, the easier it becomes to evaluate your options and find the right space for your business.

A quick way to remember it:

• Rentable Square Feet (RSF): The square footage you pay rent on.

• Usable Square Feet (USF): The space your business actually occupies.

• Leasable Square Feet: Space that's currently available for lease.

If you have questions about square footage, load factors, or lease calculations, I’m always happy to help.