Most building owners trust the square footage numbers they have on file. The figures came with the property, pulled from original blueprints, an old appraisal, or a broker’s listing sheet, and no one has had a reason to question them. But square footage calculations are only as reliable as the methods and data behind them, and in commercial real estate, even a small discrepancy compounds into real money over time.

Where Square Footage Numbers Come From and Where They Go Wrong

Inaccurate square footage usually traces back to a few common sources. Original architectural drawings reflect what was designed, not necessarily what was built. Renovations shift walls, reconfigure layouts, and add or remove space without anyone updating the official records. Different appraisers and property managers measure using different methods, producing numbers that don’t align. And in many cases, the figures on file are simply rough estimates that were never verified in the first place.

The problem grows as buildings age. A property that has changed hands multiple times and gone through several rounds of tenant improvements can carry square footage numbers that bear little resemblance to the actual space.

The Financial Impact of Getting It Wrong

Wrong numbers rarely stay contained to one line item. Inaccurate square footage calculations ripple across leasing, operations, taxes, and long-term planning in ways that are easy to overlook until they add up.

Lost lease revenue. If the rentable square footage of a building is understated, the owner collects less rent per floor than the space actually supports. Multiply that shortfall across every lease on every floor, and the annual revenue loss adds up quickly. Owners who commission accurate square footage calculations frequently discover they have been leaving money on the table for years.

Tax and insurance exposure. Square footage figures flow into property tax assessments, insurance policies, and operating expense allocations. Overstated numbers can inflate tax bills unnecessarily. Understated numbers may leave a building underinsured, a risk that only becomes visible after a loss event.

Renovation and space planning errors. Architects and designers who base their work on inaccurate floor plans face budget overruns, material waste, and costly change orders once they encounter conditions that don’t match the drawings.

Property valuation discrepancies. Commercial properties are commonly valued on a price-per-square-foot basis. If the square footage is wrong, every calculation built on that number, from acquisition pricing to refinancing terms to portfolio assessments, starts from a flawed foundation.

Why BOMA Calculations Are the Industry Standard

The Building Owners and Managers Association (BOMA) publishes measurement standards that define how commercial space should be classified and calculated. BOMA calculations provide a consistent framework for determining usable area, rentable area, common areas, and building amenities so that owners, tenants, brokers, and appraisers are all working from the same set of rules.

This consistency matters because square footage is not a single number. The same building produces different figures depending on whether you measure the usable area within a tenant’s walls or the rentable area that includes a proportional share of common spaces like lobbies, corridors, and restrooms. BOMA standards define exactly how these categories are measured and allocated, removing ambiguity from lease negotiations and financial reporting.

BOMA has also updated its standards over time. A building measured under an older version may carry numbers that no longer align with current methodology. Periodic remeasurement ensures that a property’s records reflect the most current and defensible calculations available.

When to Commission a Professional Measurement

Certain moments in a building’s lifecycle make accurate square footage calculations especially important: before signing new leases, before a major renovation, during acquisition or disposition, when operating expenses seem disproportionate to the space, or when existing records are outdated or of unknown origin.

A professional BOMA-compliant measurement is a relatively modest investment compared to the ongoing cost of operating with wrong numbers. The resulting documentation gives owners a verified, defensible baseline that supports better financial decisions across leasing, operations, and capital planning.

Getting the Numbers Right

The longer a building operates on unverified square footage, the more those inaccuracies cost. A single professional measurement can correct years of compounding errors and give owners a reliable foundation for every financial decision tied to the property.

Architectural Resource Consultants (ARC) provides professional space accounting and BOMA-compliant square footage calculations as part of its nationwide building documentation services. With more than 25 years of experience documenting existing conditions, ARC helps clients replace assumptions with accurate records. Learn more at arc-corporate.com.