What Is BOMA Square Footage Measurement?

BOMA square footage measurement is a standard way to measure commercial office space so landlords, brokers, and tenants can describe area consistently. If you market suites, negotiate leases, compare stacking plans, or prepare a tenant improvement package, understanding the BOMA method helps you avoid confusion about what area a tenant actually occupies and what area they also help support through common building space.

In plain English, BOMA square footage measurement is mostly about office buildings and rentable area. It is different from residential measuring methods and different from the way many people casually talk about square footage. In California, where lease economics, common area load factors, and permit-ready documentation often need to line up, BOMA can be a practical framework—but it only works well when the underlying field measurements are accurate.

What BOMA square footage measurement means

BOMA stands for the Building Owners and Managers Association. In commercial real estate, the BOMA standard office measurement method is used to determine areas such as usable square footage and rentable square footage in office buildings. The goal is not just to measure walls on a floor plan. The goal is to create a consistent measurement system that supports leasing, planning, and building operations.

At a high level, BOMA square footage measurement helps answer questions like these:

• How much space can a tenant actually use within a suite?
• How much of the building’s shared area is allocated to that tenant?
• What area should appear in lease marketing and lease calculations?
• How should multiple suites on the same floor be compared fairly?

That last point matters a lot. Two office suites can feel similar when you walk them, but their rentable areas may differ because of building common areas, floor common areas, and how the building is laid out. BOMA is meant to bring order to that process.

Why BOMA matters in office leasing

For office landlords and brokers, square footage is not just a technical detail. It directly affects asking rent, lease comparisons, test fits, and occupancy costs. If rentable area is overstated or inconsistently measured, negotiations can stall or create distrust later. If usable area is misunderstood, a tenant may believe a suite fits a headcount or furniture plan when it really does not.

BOMA square footage measurement is especially useful when you need consistency across a building or portfolio. It can help with:

• Listing office suites with a recognized industry measurement basis
• Comparing different vacancies on the same floor or in the same building
• Preparing lease outline drawings and stacking plans
• Supporting tenant improvement planning before permit drawings begin
• Reducing arguments over load factors and rentable area assumptions

If you are also reviewing whether you need measured existing conditions before leasing or construction, our guides on commercial landlord drawing needs and lease outline drawings provide useful context.

Usable vs rentable area under the BOMA approach

The clearest way to understand boma square footage measurement is to separate usable area from rentable area.

Usable area

Usable area is the space a tenant can physically occupy and use for its own operations. In an office setting, that usually means the suite interior area intended for that tenant’s desks, offices, meeting rooms, reception, storage, and similar functions. It does not simply mean “everything inside the building.”

Rentable area

Rentable area takes the usable area and adds the tenant’s proportionate share of certain common areas. In office buildings, tenants do not occupy the lobby, public corridors, restrooms serving common areas, or other shared support spaces exclusively, but those spaces support the tenancy. BOMA measurement allocates an appropriate share of those areas so the total rentable figure reflects both private and shared use of the building.

This is why a tenant’s rentable square footage is usually larger than its usable square footage. The difference is often described as a load factor, add-on factor, or loss factor, though the exact terminology in practice can vary.

For a deeper look at how these concepts differ in leasing conversations, see rentable vs usable square footage explained.

How BOMA measurement is typically applied in practice

While the formal BOMA standard is detailed, the practical workflow usually starts with reliable field dimensions. You need an accurate base drawing of the floor plate, suite boundaries, major penetrations, corridors, common areas, and building core elements. Without that, even a well-intentioned BOMA calculation can be off.

In practice, a typical process includes:

• Measuring the existing building or floor with on-site laser measurement
• Drafting accurate CAD floor plans from field data
• Identifying tenant areas, floor common areas, and building common areas
• Applying the selected BOMA office measurement rules consistently
• Producing drawings and area schedules that brokers, landlords, or design teams can use

FastAsBuilt supports this front end of the process by field-measuring existing conditions across California and producing permit-ready CAD files in PDF and DWG format. For office, retail, warehouse, and other commercial spaces, that accurate measured baseline is often what makes later square footage analysis dependable.

If your building is headed toward a tenant improvement, a lease negotiation, or a change in occupancy review, measured existing plans are often the first step. Related reading: as-built drawings for commercial buildings and whether as-built drawings matter for a commercial lease.

What is included in a BOMA standard office measurement review

The BOMA standard office measurement framework is more than tracing suite walls. A proper review usually looks at how the entire office floor functions and how shared space should be distributed. Depending on the building, this may include:

• Suite perimeter and interior demising lines
• Building core areas such as elevators, stairwells, shafts, and mechanical rooms
• Public corridors and floor service areas
• Lobbies and other shared circulation spaces
• Vertical penetrations and major exclusions
• Multi-tenant vs single-tenant floor conditions

It also requires clarity about the purpose of the measurement. Are you using it for marketing? For lease drafting? For a test fit? For lender or asset management reporting? Different stakeholders may need the same measured floor plan but use it for different decisions.

That is one reason many property teams first order accurate existing condition plans and then layer in lease analysis, planning, or design work afterward. If you need measured plans for an office suite or building, you can review FastAsBuilt’s packages to compare 2D and 3D options.

BOMA vs ANSI: what is the difference?

The boma vs ansi question comes up often because both standards deal with square footage, but they are used in different contexts. ANSI is commonly discussed in residential settings, especially single-family homes and appraisals. BOMA is associated with commercial office measurement and lease economics.

Here is the short version:

• BOMA: Primarily used for commercial office buildings, especially to determine usable and rentable area.
• ANSI: More commonly used in residential measurement conversations and other contexts where gross living area or similar concepts matter.

The standards are not interchangeable. A landlord should not assume that a measurement prepared under a residential framework will satisfy office leasing needs. Likewise, a residential appraiser’s square footage discussion is not the same thing as a BOMA rentable area analysis.

For readers comparing methods across asset types, our article on ANSI square footage measurement explains where that standard fits.

In California practice, this distinction matters because many owners have mixed information sources: old permit plans, marketing flyers, previous tenant plans, and occasionally residential-style area assumptions for mixed-use property. Before using any number in a lease or broker package, confirm the measurement basis and whether it actually reflects office leasing standards.

Common mistakes landlords and brokers make with office square footage

Most square footage disputes do not come from bad intent. They come from inconsistent source documents, old plans, or assumptions carried forward for years. A few recurring issues are worth watching for.

• Using outdated drawings: Prior tenant improvements may have shifted walls, expanded corridors, or changed common area layouts.
• Mixing measurement standards: Numbers taken from marketing flyers, appraisal documents, and permit plans may each have a different basis.
• Confusing usable and rentable area: A tenant may focus on the space inside the suite, while the lease quote uses a larger rentable figure.
• Skipping field verification: Existing CAD files are helpful, but they should not be treated as correct unless verified against actual site conditions.
• Ignoring altered building conditions: Demising changes, added amenities, and circulation updates can affect how area should be allocated.

These issues are especially common in older California office stock, adaptive reuse projects, and buildings with many rounds of tenant improvements. If plans are unreliable, getting current as-built drawings can save time before lease drafting or design starts. Our related guide on how to get as-built drawings for an office build-out walks through that process.

When you need accurate field measurements before applying BOMA

BOMA calculations are only as reliable as the measured conditions beneath them. If your office suite or building has not been field-measured recently, it is smart to update the base plans before relying on square footage for leasing or construction decisions.

You should strongly consider new measurements when:

• You inherited old landlord plans with unknown accuracy
• A suite has been reconfigured by one or more prior tenants
• You are marketing a vacancy and want consistent lease figures
• You are preparing a tenant improvement or permit package
• You are combining or subdividing suites
• You are evaluating an office-to-other-use conversion concept

FastAsBuilt provides field-measured as-built drawings and measured floor plans throughout California, with local crews serving Los Angeles, Orange County, the Inland Empire, the Bay Area, and San Diego. We use on-site laser measurement, and senior drafters produce permit-ready CAD files delivered in PDF and DWG formats.

For straightforward existing conditions documentation, 2D As-Built Plans start at $900 for up to 1,500 square feet, then $0.50 per square foot, include one revision, and are typically delivered in 48 to 72 hours. For projects that also need a model and additional drawing views, 3D As-Built Plans start at $1,500, then $1.00 per square foot, and include a 3D model plus 2D floor plans, elevations, and sections, with two revisions and typical delivery in 3 to 5 business days. Custom commercial projects, including tenant improvements, are quoted individually.

Turnaround times are estimates and may vary based on project complexity and scheduling.

How BOMA measurement connects to leases, TI work, and due diligence

Office square footage does not live in a vacuum. It affects several stages of a commercial real estate deal and project lifecycle.

Leasing and renewals

During leasing, BOMA-based area figures can shape quoted rent, operating expense allocations, and side-by-side comparisons with competing spaces. A clean measurement record can also reduce back-and-forth during renewals or expansions.

Tenant improvements

During TI planning, measured existing conditions support test fits, furniture plans, life-safety coordination, and eventual permit drawings. If the square footage basis is unclear at the start, downstream drawings may also become less reliable. Our resource on as-built drawings for commercial tenant improvements goes deeper on that workflow.

Acquisition and asset management

For buyers, owners, and asset managers, consistent office measurements help with underwriting assumptions, vacancy reporting, and capital planning. They also help you understand whether historical area figures still reflect the building as it exists today.

In California, always remember that square footage measurement and code compliance are separate questions. A BOMA review does not replace permit review, ADA evaluation, fire-life-safety review, or Title 24 analysis. If a project moves toward construction or occupancy changes, confirm local jurisdiction requirements with the city or county and your licensed design professionals.

California-specific considerations for office properties

California office owners and brokers often work in buildings that have evolved over time. Multi-tenant floors may have been re-demised repeatedly. Amenity spaces may have been added. Historic structures may carry older drawings that do not match current conditions. That makes accurate measurement especially important.

A few practical California considerations include:

• Older urban office stock: Downtown and legacy suburban buildings may have incomplete or outdated record drawings.
• Frequent TI activity: California office suites are often reworked between tenants, changing walls, support areas, and circulation.
• Permit coordination: If marketing turns into construction, measured plans can become the base for permit-ready drafting.
• Mixed-use buildings: Owners should be careful not to blend residential and commercial measurement assumptions.

For landlord and broker teams, the practical takeaway is simple: use a recognized office measurement framework, and make sure the floor plan behind it reflects actual field conditions. That combination gives you a stronger basis for leasing discussions and project planning.

Frequently asked questions

Is BOMA square footage measurement required for every commercial lease?

No. Not every lease legally requires BOMA measurement, and parties can define area in different ways by agreement. But BOMA is widely used in office leasing because it creates a familiar, consistent basis for comparing suites and allocating shared space. You should confirm the measurement basis in the lease and make sure everyone is using the same definition.

Does BOMA apply to all commercial property types?

BOMA is strongly associated with office measurement. Other commercial property types may use different conventions depending on the asset, market, and purpose of the measurement. If you are dealing with retail, industrial, restaurant, or mixed-use space, it is wise to confirm which standard or lease definition is actually being used before relying on a square footage figure.

What is the main difference between BOMA and ANSI?

The main difference is context. BOMA is commonly used for office leasing and focuses on usable and rentable area. ANSI is more commonly discussed in residential measurement contexts. If you are measuring office suites for leasing, BOMA is usually the more relevant framework. If you are evaluating a home or residential area calculation, ANSI is more likely to come up.

Can existing permit plans be used for BOMA calculations?

Sometimes, but only if they are accurate and current. Permit plans may not reflect later tenant improvements, field changes, or revised demising lines. Before applying a BOMA standard office measurement analysis, it is smart to verify the plans against actual site conditions, especially in older California office buildings or recently vacated suites.

Do you need as-built drawings before measuring office square footage?

In many cases, yes. If your current plans are incomplete, outdated, or missing, field-measured as-built drawings are often the best starting point. They provide a reliable base for lease outline drawings, BOMA area studies, TI planning, and permit-ready coordination. They are especially useful when a building has gone through multiple remodels or tenant turnover cycles.

Bottom line

BOMA square footage measurement is the standard office-language tool for describing how much space a tenant uses and how much shared building area is allocated to that tenancy. For California landlords, brokers, and property teams, it is most effective when paired with accurate field-measured plans. If you need dependable existing conditions for office leasing, TI planning, or area verification, FastAsBuilt can provide measured floor plans and permit-ready CAD files across California.