Commercial Office Space Measurement

“Give an inch take a mile… I wouldn’t touch it with a ten foot pole… a miss is as good as a mile… he won’t budge an inch.”

There are all kinds of metaphors for measurements and some are really confusing. Well, commercial office space measurement can be just as confusing. What I will try to do in this article is give a somewhat clearer understanding of the current method of commercial office space measurement and offer some key terms that go along with the measurement of space.

For as long as I have been in the business, the generally accepted practice for measuring office space is called the BOMA Standard.  (BOMA is an acronym for the commercial group known as Building Owners and Managers Association.)  It is noted that this standard can be, and is, recommended for usage when measuring office space in both old and new buildings.

Now let’s look at some key terms that are used in the measurement of commercial space.


I like to refer to the useable area of an office space as the area a tenant actually uses or occupies, or the area that a tenant uses to house equipment and personnel. The useable area of an office can vary over time in a multi-story building because corridors change as floors are remodeled. When computing the useable area, one can start by measuring to the finished surface side of the office side of the corridor or other permanent walls, to the center of the devising walls that separate the office area from the adjacent useable area, to the inside finished surface area of the outer building walls. There are no deductions made for columns or projections necessary to the building.


I like to refer to the rentable area of an office space as the useable area of a tenant plus the common area of the entire floor the tenants occupy, excluding elements that penetrate through the floor such as electrical and plumbing chases, elevator cores, vertical ducts, stairwells and flues. When calculating the rentable area of an office, one must measure the inside finished surfaced area of the permanent outer walls, excluding any vertical penetrations of the floor.


The building common areas include the areas of a building that are used to service the tenants of a building, such as common lobbies, corridors, security desks, vending areas, common conference rooms and common restrooms, and are not included in the office area of a particular tenant. These areas are also added to the floor rentable area to calculate the rentable area.


The load factor of a building floor is the percentage of the area on a floor that is not useable, typically the common area and is used when converting a useable area to a rentable area.

Conversion Formulas:

Rentable Area divided by Useable area = R/U Ratio

Useable Area x R/U Ratio = Rentable Area

Rentable Area divided by R/U Ration = Useable Area

Useable Area x (1 + Load Factor) = Rentable Area


For measurement purposes, the finished surface is the finished partitioning wall excluding the thickness of special surfacing. It is basically the finished sheet rock wall or glass wall, whichever the case may be.


Also known as dominant portion, permanent outer space is the inside finished surface of the permanent outer building wall.


As stated above in rentable area, vertical penetrations are typically electrical and plumbing chases, elevator shafts, stairwells, vertical ducts that service more than one floor of a building.

Hopefully, the above information helps one develop a clearer understanding of how office space is measured, particularly when it comes to determining the square footage of an office area


Donnie Laurens
Commercial Real Estate Agent
Macon Commercial Office