Usable vs. Rentable Space — Why it Matters

Jun 29, 2022 10:00:00 AM / by Julie Nguyen


For tenants seeking office space, it is important to distinguish between common terms used to determine square footage. You’ll often come across different terms describing the square footage, such as gross square footage, usable square footage, or rentable square footage.

Usable square footage and rentable square footage are not interchangeable terms and understanding the differences will elucidate important factors you should be considering when signing an office lease.

Usable square footage

Usable square footage (USF) is the floor space that you will use and occupy exclusively. This includes any private restrooms, storage spaces, or janitorial closets that are unique to your office. When determining how much space you’ll need for your business, keep in mind the USF.

Calculating usable square footage

Calculating the USF is intuitive. To determine USF, calculate the area of the space you will occupy. For example, a rectangular office space with dimensions 20ft by 10ft will have a USF of 2000ft2.

Rentable square footage

Rentable square footage (RSF) includes the USF plus a percentage of the floor space in common/shared areas. Common/shared areas may include elevator lobbies, shared bathrooms, hallways, and cafeterias. As a result, the RSF will appear larger than the amount of space you will be occupying.

Calculating rentable square footage

Although the landlord may already provide the RSF, you may calculate it yourself to check if the RSF was appropriately determined. To calculate RSF, first determine the USF. Then, determine the percentage of shared space in the entire building, otherwise known as the load factor. Next, multiply the load factor by the total amount of shared space to yield your proportion of shared space. Finally add your USF to your proportion of shared space to obtain your RSF.

For a more concrete example, an office building has a gross square footage of 10,000ft2 with 4 suites, each at 2000ft2, leaving 2000ft2 of shared space. If you lease one suite, your USF is 2000ft2 and the load factor is 20%. Multiplying 20% by 2000ft2 of shared space yields 400ft2 of shared space that will add towards your RSF. Therefore, the USF, 2000ft2, plus your portion of shared space, 400ft2, totals 2400ft2 of RSF.

Why Terminology Matters

Distinguishing between USF and RSF will help you determine how much space is available for your own use and how much common space you’ll be sharing. It is important to pay attention to the USF when seeking ample space for your office; however, note that the total rent is determined by the RSF. Office buildings with massive elevator lobbies or large bathrooms are likely to inflate the RSF, leading to increased rent. It is imperative that landlords be transparent in everything included in the RSF. Be sure to request additional details should this information not be readily available. Ideally, you’ll rely on a commercial real estate broker to tackle these details and help you through negotiations. Reach out to Aspect Real Estate Partners if you are currently seeking an office in Orange County so that we can help you locate the best office space.

Topics: Commercial Real Estate, Resources

Julie Nguyen

Written by Julie Nguyen