BOMA measurement standards for office space are the industry rules, published by the Building Owners and Managers Association, that translate the physical footprint of a suite into the square footage you actually pay rent on. The critical move is this: BOMA takes the space inside your walls (usable area) and adds a proportional share of the building’s lobbies, corridors, restrooms, and mechanical rooms to produce a larger figure (rentable area). Rent is calculated on the larger number. The ratio between the two, called the load factor, is where most of the money in a lease negotiation quietly lives.
The current office edition is ANSI/BOMA Z65.1-2024, which replaced the 2017 version.1BOMA International. BOMA Standards The version written into your lease governs your space, so a building leased under the 2017 or an earlier standard is still measured that way even though a newer standard exists.
Usable Area Versus Rentable Area
Usable area is the space where you put people and furniture. It generally runs from the office side of the corridor wall to the inside finished surface of the exterior glass. Where a wall divides two neighboring suites, the measurement goes to the center of that wall so each side gets a fair split.
Rentable area is usable area plus your proportional share of the building’s common spaces: lobbies, shared corridors, restrooms, mechanical rooms, and similar areas that every tenant benefits from but nobody exclusively occupies. Rentable is always larger than usable, and rent is calculated on rentable.
There is also a gross building area figure, used mostly for tax assessments and construction estimates rather than leases. Interior Gross Area measures to the inside face of the exterior walls and excludes major vertical penetrations such as elevator shafts and stairwells. BOMA defines a major vertical penetration as any floor opening larger than one square foot that serves vertical building systems.2BOMA International. BOMA Floor Standards Interpretations Documents Best Practice Guidance Exterior Gross Area measures to the outside face of the exterior walls.
How the Load Factor Drives Your Rent
The load factor is the ratio of rentable area to usable area. Divide total rentable by total usable and you get a number like 1.25, which means you pay for 25 percent more square footage than you physically occupy. That 25 percent covers your share of the building’s shared spaces. The percentage above 1.0 is sometimes called the add-on factor.
A tenant with 10,000 usable square feet in a building with a 1.25 load factor pays rent on 12,500 square feet. Office load factors generally fall between 1.20 and 1.50, with the higher end common in older buildings or buildings with large lobbies and extensive shared amenities.
The load factor also determines whether two “identical” suites are actually identical. A suite advertised at 5,000 rentable square feet in a building with a 1.20 load factor gives you roughly 4,167 usable square feet. The same 5,000 rentable feet in a building with a 1.40 factor gives you only about 3,571 usable feet. Same rent bill, 600 fewer square feet of actual workspace. Ask for the load factor before you compare quoted rents across buildings, because the per-usable-foot cost can differ sharply from the per-rentable-foot cost the broker shows you.
Method A and Method B
Since the 2010 standard, and carried forward through 2017, buildings are measured under one of two calculation methods. The owner picks one and applies it to the whole building; the two cannot be mixed in the same structure.
Method A, the legacy method, produces different load factors for multi-tenant floors and single-tenant floors. A tenant on a multi-tenant floor sees the factor shift if the shared corridor grows or shrinks. This is the more widely used method and tracks the traditional approach.
Method B applies one uniform factor across every floor, treating all floors like multi-tenant floors. The factor stays the same regardless of how any individual floor is configured.
The building’s total square footage is the same under either method. What changes is how that total is distributed among tenants. Method A tends to favor tenants who occupy an entire floor, because they avoid picking up common corridor costs that don’t exist on their floor. Method B spreads costs evenly, which is simpler but can feel less fair to full-floor occupants. If you’re taking a full floor, find out which method the building uses before you finalize numbers.
Which BOMA Version Applies to Your Lease
Different editions of the standard can produce different rentable figures for the same physical space, so the edition named in your lease is not a technicality. It controls the number your rent is calculated on.
The 2017 standard (ANSI/BOMA Z65.1-2017) is still the reference for many leases currently in force. It expanded the space classification system into categories including occupant areas, building amenity areas, building service areas, floor amenity areas, floor service areas, parking, and occupant storage. It also clarified that truck courts, loading docks, and enclosed rooftop mechanical penthouses should be included in the overall measurements, and it changed the treatment of outdoor space: balconies count as tenant area, while ground-level patios are only included if they qualify as part of a covered gallery.
For new buildings, or buildings measured for the first time, the 2024 edition is the current one. If your lease specifies an older edition, that edition governs even though newer standards exist. Confirm the edition in writing before any remeasurement, because a building recalculated under a different standard can produce a rentable figure that no longer matches the one you agreed to.
Negotiating and Locking In the Measurement
Tenants have more room to push back on measurement terms than many realize. A few approaches experienced tenants use:
- Ask for the building’s BOMA measurement report showing usable and rentable figures for your suite and the building overall. A landlord who won’t share it is telling you something.
- Negotiate a cap on the load factor so future remeasurements or building modifications can’t quietly increase your rent obligation.
- Specify which BOMA edition applies, and hold that version constant for the term of the lease.
- Fix the square footage at signing. Some leases state that the premises will not be subject to remeasurement, meaning the agreed-upon square footage stays constant regardless of later adjustments.3BOMA International. Green Lease Guide
Some leases include a remeasurement clause allowing the landlord to remeasure at specified points, such as after demising walls are installed or after a renovation. Landlords tend to remeasure when doing so would increase a tenant’s obligations rather than decrease them, so tenants who want stability should push for a fixed-measurement clause during negotiations.3BOMA International. Green Lease Guide
Verifying Your Space and Handling Disputes
Disagreements over measurement usually come down to how a space was categorized or where a boundary was drawn. BOMA’s own guideline: a difference of two percent or less between two independent measurements is acceptable. When the gap exceeds two percent, a third party should resolve it.
If you suspect your rentable figure has been overstated, don’t try to verify it by counting ceiling tiles or pacing rooms. Those estimates are not accurate enough to support a real dispute and can undermine a legitimate concern by making you look unprepared. Hire your own measurement firm to produce an independent BOMA-compliant analysis. Comparing two professional measurements on equal footing is the fastest way to close the disagreement.
One thing to know about who does the measurement: BOMA does not certify, approve, or endorse any individual or firm for measurement purposes, and it does not require a specific licensed professional to perform the work.2BOMA International. BOMA Floor Standards Interpretations Documents Best Practice Guidance In practice, owners hire architectural firms or specialized measurement consultants, and the firm itself certifies the accuracy of the final calculations. When you hire your own, get the scope of work in writing and confirm which BOMA edition the firm will apply.
If Your Building Isn’t Purely Office
The office standard covered here does not apply to every commercial building. BOMA publishes separate standards for other property types, each tailored to that type’s characteristics:1BOMA International. BOMA Standards
- Industrial and flex buildings: ANSI/BOMA Z65.2-2025
- Retail properties: ANSI/BOMA Z65.5-2025
- Mixed-use properties: ANSI/BOMA Z65.6-2021
- Multi-family and hospitality: ANSI/BOMA Z65.4-2023, which includes both a Gross Area Method and a Net Area Method
If your space sits inside a building that combines office, retail, and residential uses, the mixed-use standard applies rather than the office standard. Each standard handles common areas and load factors differently, and a measurement performed under the wrong one can produce numbers that don’t match what the lease requires.