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BOMA: The Standard For Measuring Office Space

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In most parts of the country, the most common method for measuring office space and determining the gross leasable area is the BOMA (The Building Owners and Managers Association) standard. It is the most commonly used method as it provides Landlord’s with the ability to capture all common areas when calculating rentable square footage. The 1980 standard analyzed tenant spaces by floor while the 1996 method took into account the entire building’s rentable square footage.

In Silicon Valley, the BOMA standard is most commonly used while a number of office buildings use the Drip-Line method which determines the rentable square footage where the measurement is taken to the outermost perimeter of the building, regardless of whether it is enclosed or not.

In addition, there are some methods of measurement based on regional standards. Two of these regional standards are the REBNY and GWCAR methods, which are commonly used in the New York City and Washington D.C. area, respectively. The REBNY method attempts to bring the rentable square foot number as close to the gross built area so that they can maximize profits.

Regardless of what measurement method is employed, it is advisable that tenant’s perform proper due diligence before executing a lease to ensure they are getting what they pay for. While smaller tenants may not have the leverage that a 100,000 square foot user has, they should ensure that the rentable square footage of their space is at the very least within close proximity of what the landlord is quoting.

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23 Comments (Open | Close)

23 Comments To "BOMA: The Standard For Measuring Office Space"

#1 Comment By Michael A. Mandel On July 28, 2008 @ 1:59 pm

A note on NYC office space and REBNY. REBNY does not actually offer a definition for “rentable” sf. Generally rentable sf in NYC is not equal to gross built area, it exceeds it! REBNY does define “usable” area however, and that definition includes the space out to the outer edge of the building (including the brick and windows).

For more on this, check out: [7]



#2 Comment By KEV. On July 29, 2008 @ 10:21 am

You should to do a write up about the definition of Usable SF Vs Gross SF Vs. Rentable SF and how load factors are applied – you can even give some mathimatical examples. I know there’s alot of people out there who dont understand this.

#3 Comment By Lloyd On June 2, 2009 @ 5:28 am

I have a question:

In order to measure ground floor retail space in Boma Standards, is the measurement taken from the middle of the outside wall? Please let me know.

Many Thanks,


#4 Comment By squarefeet On June 2, 2009 @ 7:48 am

retail space is generally measured from the outside face of the wall. If the retail space is in-line, or shares a wall with another tenant, then those shared walls are measured from the center line.

Remember though that some landlords measure using BOMA dripline, which can go beyond the exterior wall and measure to the outside perimeter of the building (which may not be the exterior wall).

In retail, size is generally referred to as GLA, which is gross leasable area. That area too is also measured to the outside face of the wall, and center line of common walls.

#5 Comment By Jonathan Pollack On July 7, 2009 @ 1:42 pm


Here is a small write up on Usable SF Vs Gross SF Vs. Rentable SF and how load factors are applied.

Let me first say these definitions are all subject to change depending on how the lease document is written. However, the ANSI/BOMA Z65.1-1996 which is the most current BOMA standard and generally accepted nationally defines them as follows:

Usable Area: The measured area of an office area, store area, or building common area on a floor. The total of all the Usable Areas for a floor shall equal Floor Usable Area of that same floor.
In english this means when you measuring your office it is the area you can touch, put a desk or a chair(usable). Depending on the office you may measure from the glass or the wall. No deduction for pillars or support beams.

Gross Building Area: The total constructed area of the building. Generally not used for leasing purposes.

Gross Measured Area: The total area of a building enclosed by the Dominant Portion, excluding parking areas and loading docks outside the building line Generally not used for leasing purposes.

Rentable SF: I think Boma does a very poor job of defining this in straight forward terms. They define it as Rentable SF = Usable Area x R/U Ratio.

What that means if you drill it down is basically your Usable SF + your % of the common area for the floor + your % of the common area of the building equals your rentable SF. The R/U Factor is your Load Factor. Therefore you must know the Rentable SF of the floor and of the entire building.

You should also know there are certain rules on what is included and what is not. Every building is different and some don’t jive into the BOMA standard exactly right.

I hope this was insightful, if you have any questions feel free to e-mail me [9]

#6 Comment By Jonathan Pollack On July 7, 2009 @ 1:50 pm


I all depends on your lease. Sometimes the lease spells out exactly how to measure the space. It may say the landlord used BOMA standards. If the lease is silent in explaining the method of measurement then it is BOMA by default, unless in NY or DC.

if you have any questions feel free to e-mail me [9]

#7 Comment By BT On July 16, 2009 @ 7:57 am

How does Restrooms, stairwells, and elevators calculate into Rentable area vs ANSI/BOMA office area?

#8 Comment By Jonathan Pollack On July 29, 2009 @ 9:09 pm


I am not sure what you mean when you say “Rentable area vs ANSI/BOMA office area.” However, according to the current BOMA ANSI standard here is how the areas are defined.

Restrooms are considered apart of floor rentable area if connected to the tenants floor via a climate controlled corridor. Unless the bathrooms serve the entire building in which case they are building rentable area.

Stairwells and elevators are consider vertical penetrations and are not considered rentable area.

I hope this answers your question. If you need further clarification feel free to contact me. [10]

Best Regards,

#9 Comment By David Aube On October 6, 2009 @ 5:51 am

Hey all, I have written a very detailed explanation of the REBNY code and noted the main differences between the REBNY and BOMA standards. It can be viewed at [11]

For a bunch of other information, just browse my site: [12]

Dave Aube

#10 Comment By Jay On March 10, 2010 @ 9:45 pm

I have a quick question regarding the square footage measurement of a practice we just acquired. Basically, the Gross SF of the first floor is 7,500 SF, the Interior Gross Area as defined by ANSI/BOMA “Office Buildings: Standard Methods of Measurement and Calculating Rentable Area”; promulgated
by the Building Owners and Managers Association, date 2010, is 7,190. The architect is simply saying that the difference here is the measurement from the outside walls being included on the Gross SF, but not being included on the IGA SF.

Which way is correct for this single-tenant occupancy? Any help here would be appreciated.

#11 Comment By Brad Augustine On April 18, 2010 @ 7:43 pm

BOMO uses the term RENTABLE and my Starbucks Lease uses the word LEASABLE. Is there a difference or do they have the same deffinition?

#12 Comment By Square Feet On April 19, 2010 @ 8:11 am

BOMA is primarily for office. Leasable is a term more common in retail leasing. In general, retail spaces are measured from the outside of the premises on exterior walls, and to the midpoint of any demising walls. Of course, the lease could define the term Leaseable to mean anything. As of a year or two ago, ICSC and BOMA were working on a retail standard, though not sure that's been finalized yet.

#13 Comment By Michelle On July 10, 2010 @ 11:09 am

I am trying to determine the Gross Building Area of a two level brick office building. The office building is a brick rectangle. One enters the front glass doors onto the first level. The catch is that the building is on a waterfront lot and the middle of this first floor is open on the back side. There is a four foot brick wall but approximately 1/2 of this center area of the 1st floor is an open breezeway, with vinyl ceilings, recessed lighting, carpet and ceramic tile and accesses to two retail spaces, the elevator, public restrooms, office space. It plays as a building lobby and does have utiltiies and maintenance associated with it yet it is open on the rear side and enclosed by glass doors on the front side. The perimter of this level has three seperate office suites and four garage bays. The second level of the building is fully enclosed and leasable space. My question: Would this open breezeway area be included in the Gross Building Area calculation? I would think ‘yes’. The space is leased out for parties from time to time as it is a waterfront site w/ a marina. In developing an income approach for appraisal purposes, would this area be included as leasable space?
Thanks for any input.

#14 Comment By Lawrence Speight, P.E. On August 3, 2010 @ 1:28 am

The answer is simple. Disregard any space that is access area, area waiting area, enjoying the sea breass area, and unsecured when every goes home at night. Take a tape measure and measure the INSIDE dimensions of every space within the permit area you are dealing with. Perhaps your client needs my help in describing his property subject to a particular lease. At any rate the area I have asked you to measure is the basis for your lease and that is what should be the base point in any discussions regarding the rent and/or occupancy of this property. My suggestion is simple but crutial to the sucess of you transaction.
Give me a call at (760) 223-6276 to explore this further should you wish.

Lawrence Speight, P.E.
General Contractor and Engineering Contractor

#15 Comment By Tanya Anderson On September 24, 2010 @ 10:51 am

What is the difference between Legacy A and Method B in calculating office space. We are looking to lease a space and the sq. footage of the actual office space is approx 5400 sq ft but they are coming up with 6371 sq ft. They state theya re using BOMA standards which allows them to include a portion of the lobby area. The lobby area is share by all 3 floors with multiple tenant space on each floor. The difference in our lease area (5400) and their calcualtions (6371) is 971 sq ft. The lobby isn’t even that big. If I added in the public restrooms it may equal that uch but hten that would mean that we were paying for the entire area not just a portion of it. Can you please advise?

#16 Comment By janet On December 29, 2010 @ 9:14 pm

what typical items are deducted from an office buildings gross area when calculating usable/rentable area?

#17 Comment By Brien Wloch On March 16, 2011 @ 6:47 am

I’m still a little confused. If I have 6,000 sf of gross floor area in an office building and I have 3,000 sf. of rentable space and 3,000 sf of common area (lobby and restrooms), an elevator core and stairs, and the market rent is $15 psf and the tenant wants a 1000 sf space where he can put desks and things, how much rent should he pay? For example, does he pay for his 1,000 sf + 1/3 of the remaining area or $15 x 2,000 sf or $30,000 per year or is it calculated differently?

Thanks in advance for your help.

#18 Comment By ADDARC On September 9, 2011 @ 10:39 am

Hello all.

Brien, in your example, the tenant would pay for 1,000 sf (Useable) + 1/3 of the remaining space (Floor common) on the floor (jan closet, bathrooms, hallways, common area, BUT DOES NOT include shafts such as stairs or elevator shafts) + their proportionate share of any main lobby, mail area, mechanical space, etc. That all comes out to a very small % depending on # of tenants.

Therefore lets say there is 6,000 sf gross. The floor has 3 Tenants all with 1000sf. There is 1000 sf halls, bathrooms, janitor closet, electrical, etc and 2,000 sf shafts/stairs. So only 4,000sf of each floor can be rented! (not typical)

The building has 5 floors, 4 all exactly the same. The main floor has 2000sf of mail area, front desk, lobby, shared conference center, etc.

Your tenant would pay this:
1,000sf (their space)
+333 sf (their portion of their floor (1000/3 tenants))
+166 sf (their portion of building common (2,000/12 tenants))
=1,500 sf. they pay for.

This is not typical as most places (except NYC) have loss factors closer to 35% where this example is at 50%.

I hope this clears things up a bit for you all.

I have written a very extensive description of measuring square footage. It compares the very flimsy REBNY standard pamphlet with the BOMA and has examples as well. Please go to [11] to read! Thanks.

#19 Comment By AnnMarie Walsh On May 10, 2012 @ 7:53 am

I have a multi story building with an open interior light well on floors 2 through 5 . There is no roof on the light well / courtyard. When I measure the Construction Gross Square footage of floors 2 through 5, should I be deducting the square footage of the light well per the 1996 BOMA standard?

#20 Comment By Adele On July 19, 2012 @ 12:45 pm

What is the typical RETAIL square footage measuring method in Maryland. It’s a one story end cap, and we’ve received conflicting direction on how to do it…HELP!

#21 Comment By Bobby Saulnier On August 21, 2012 @ 5:35 am

I am renting floors 9 &10 of an 11 story building. Gross SF from exterior wall to exterior wall is 31,192 SF for both floors.
Should the following be counted in rentable square footage?
3 banks of elevators totaling 1762.5 SF (881.25 each floor)
2 stairwells totaling 644.5 SF (322.25 each floor)
Electrical closet 154 SF (77 each floor)
Chase 404 SF (202 each floor)
Janitor Closets 80 SF (40 each floor)

#22 Comment By Michele On August 21, 2012 @ 4:09 pm

I’m measuring a 5 story commercial building with 1 tenant. There are columns around the perimeter. Do I measure around the columns or cut through them? Also, the windows take up more than 50% of the wall $ have baseboard heating do I measure to the window or the baseboard heater?

#23 Pingback By the square footage dilemma: REBNY “leads” by protecting brokers, not buyers | Manhattan Loft Guy On September 29, 2013 @ 9:15 am

[…] 25-page national standard from the Building Owners and Managers Association (such as here, or here) my simple point (for now) is that there is and has been since 1987 a set of written guidelines for […]