Guides · Floor Plan Measurement
The square footage shown on Zillow, the MLS, and county records for the same home often shows three different numbers. As a homebuyer you're making one of the largest financial decisions of your life partly based on square footage. Here's how to verify the number before you make an offer.
County assessor records: Entered by county staff from building permit data. May include basements and garages. May not reflect additions or renovations. Can be decades out of date. Zillow: Pulls from county records or MLS. Inherits whatever errors those sources contain. MLS listing: Agent-entered. Some copy county records; others measure independently; a few include or exclude spaces inconsistently. The only reliable way to know is to measure the floor plan directly.
Many listings include a CubiCasa or Matterport floor plan in the listing photos or documents. If not visible, ask your agent to request one from the listing agent. If there's a Matterport tour linked in the listing, the floor plan view is accessible within the tour. For older homes without digital floor plans, your agent can request the prior appraisal (sellers may have one from purchase or refinance).
Upload the floor plan to MeasureFloorPlan.com. Trace the above-grade finished living area. Set scale from a labeled room dimension. Read the result. Takes about 5 minutes for a single-story home and 10 minutes for a two-story. You'll have your own verified estimate before making an offer.
2–5% difference: Normal variation. Note it but don't be alarmed. 5–10% difference: Investigate. Is basement included in the listing number? Unheated spaces? Over 10%: Significant concern. Ask the listing agent to clarify what's included. Factor the corrected sq ft into your offer price. You shouldn't pay above-grade prices for below-grade space.
If you discover a discrepancy after your offer is accepted but before the appraisal, you're in a better position than waiting for the appraiser to catch it. Renegotiating based on your own pre-appraisal research is less fraught. Measure first, offer with confidence.
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Start Measuring →Why do county records, Zillow, and MLS show different square footage?
Each source uses a different measurement standard or pulls from a different document. The county uses building permits, Zillow copies the MLS or county data, and MLS shows whatever the listing agent entered. Discrepancies of 5 to 10 percent are common, and finished basements are the single biggest source of disagreement.
How can I verify square footage before making an offer?
Ask the listing agent for a CubiCasa or Matterport floor plan (most modern listings have one). Upload it, trace the exterior perimeter, and set scale from a labeled dimension. You'll get an independent GLA in about two minutes.
What if there's no floor plan available?
Either order an inspection-stage measurement, request the seller's most recent appraisal report (the GLA from a prior ANSI Z765 appraisal is the most reliable single source), or rely on the listing's documented sources with a clear understanding of the variance.
What does a square footage discrepancy mean for value?
Price-per-square-foot is one of the most-used pricing benchmarks. A 100-square-foot discrepancy on a $200/sqft market is $20,000 of perceived value. Verify before bidding to avoid overpaying for square footage that isn't there.
Can I challenge the listed square footage at the offer stage?
Yes. If you have a documented independent measurement showing a smaller GLA, you can make your offer contingent on the seller's measurement matching, or simply offer based on what you measured.