Guide
How to Verify the Square Footage of a House
Check a home's square footage against the listing, county records and an appraisal, measure it yourself, and know when the gap matters.
Updated · FloorFigures
Short answer
Collect every figure with its source (the listing, the county property record card, any prior appraisal and the floor plan), then measure the outside walls yourself, level by level, leaving out the garage and porches and keeping below-grade space separate. If your number and an ANSI Z765 appraisal agree, you have your answer. If the gap is the size of a room, find the space one source counted and the other didn't. Hire an appraiser when the number decides a price, a tax appeal or a dispute.
Square footage figures for the same house routinely disagree, and the reasons are usually mundane: different methods, an out-of-date record, a basement counted in one total and not another. Verifying it means gathering the figures, measuring once yourself, and explaining the difference. An afternoon is usually enough.
- 1
Get the listed figure and its source
Write down the listing's square footage and ask the agent where it came from: their own measurement, the county record, a prior appraisal or the builder's plan, and by what method. In Colorado, the broker's square footage disclosure form already says. - 2
Pull the county property record card
Find the assessor's record for the address, usually on the county website. Note the living area, any split by level, whether a finished basement is included, and when the record was last updated. - 3
Find a prior appraisal
If you're financing, ask your lender for a copy of the appraisal. Sellers may have one from their own purchase or refinance. Check its effective date and which figures it reports. - 4
Measure the floor plan
Measure the listing or builder floor plan after checking its scale against a printed dimension. See square footage from a floor plan. - 5
Measure the house
Measure the outside walls at floor level, to the nearest inch or tenth of a foot. Split the outline into rectangles and add them up per level. - 6
Compare and explain the gap
Line the figures up as above-grade, below-grade and garage. Match any gap to a specific space, and get an appraiser if nothing explains it.
Where to find each figure
| Figure | Where to get it | What to note |
|---|---|---|
| Listing | The MLS sheet or listing page; ask the listing agent | The source and method, if stated; whether a basement is in the total |
| County record | The assessor's property record card, usually online | Living area by level, basement treatment, last update, permits for additions |
| Appraisal | Your lender, if you're financing; the seller's earlier appraisal | The effective date; above-grade and below-grade figures |
| Floor plan | The builder, the listing photos, or permit drawings | Whether it's a plan or an as-built measurement; whether the scale checks out |
| Your measurement | A tape or laser, or a measured floor plan | Each level separately; garage and porches on their own lines |
Fannie Mae has required appraisers to follow ANSI Z765-2021 for appraisals with effective dates on or after April 1, 2022, and Freddie Mac from November 2, 2023. Older appraisals may have used another method. A desktop appraisal relies on a floor plan someone supplied, and ANSI is encouraged there rather than required. See Fannie Mae's ANSI requirement.
How to measure the house yourself
Follow ANSI Z765, the standard appraisers use, and your number will be comparable with theirs. The essentials:
- Measure the outside. Each level is measured at floor level to the exterior finished surface of the outside walls (the siding or brick, not the foundation).
- Be precise. Measure to the nearest inch or tenth of a foot, and round only the final total, to the whole square foot.
- Work level by level. For an upper floor you can't reach from outside, measure inside and add the wall thickness, which you can measure at a door or window opening. If the walls stack, the upper floor often matches the lower one.
- Leave out what isn't finished living area: the garage, porches, decks, unfinished rooms and openings to the floor below. See does a garage count.
- Keep below-grade space separate. Any level that is even partly below grade is reported apart from above-grade area. See does a basement count.
- Watch the ceilings. Finished area needs a 7 ft ceiling (6 ft 4 in under beams and ducts). In a sloped room, at least half the floor must be 7 ft or more, and nothing under 5 ft counts.
A worked example: a two-story house with a finished basement and an attached garage.
| Area | Measurement | Area | Counts as |
|---|---|---|---|
| Main level | 40'0" × 28'0" | 1,120 sq ft | Above-grade finished |
| Upper level | 40'0" × 28'0" | 1,120 sq ft | Above-grade finished |
| Less: foyer open to below | 12'0" × 10'0" | −120 sq ft | Not counted upstairs |
| Finished basement | 40'0" × 28'0" | 1,120 sq ft | Below-grade finished |
| Garage | 22'0" × 22'0" | 484 sq ft | Not finished area |
| Above-grade total | 2,120 sq ft | ||
| Below-grade finished | 1,120 sq ft |
If this house were listed at 3,240 sq ft, the listing isn't wrong so much as different: it adds the basement to the above-grade total (2,120 + 1,120 = 3,240). An appraisal would report 2,120 and 1,120 on separate lines.
Reading the gap
| If the gap is about… | The likely cause | What to check |
|---|---|---|
| A few square feet | Rounding and measuring precision | Nothing; that's expected |
| The size of the basement | Below-grade space added to the total | Compare above-grade figures only |
| The size of one room | A bonus room, sunroom or enclosed porch counted by one source | Is it finished for year-round use, with a finished connection to the house? |
| The size of an upstairs opening | A two-story space counted on both floors | Count it once, on the lower floor |
| The size of the garage | A garage conversion, or a garage counted as living area | Is the space finished like the rest of the house? |
| None of these | A measuring or recording error | Measure again; consider an appraiser |
To see what a gap is worth at the asking price per foot, use the square footage discrepancy calculator. More on the causes in why square footage figures differ.
When should you get an appraiser?
Measuring yourself is enough to find out whether there's a problem. A professional measurement is worth it when:
- The number will decide a price, a renegotiation or a property tax appeal.
- You're in a dispute over a listing and need a figure from someone with no stake in it.
- The house is hard to measure: partly below-grade levels, sloped ceilings, a room over the garage, or several additions.
- Your measurement and the other figures still disagree and you can't say why.
Ask for the measurement to follow ANSI Z765-2021, with above-grade and below-grade area reported separately, so it lines up with any lender appraisal.
Checking a floor plan in FloorFigures
If you have the listing's floor plan or the builder's PDF, FloorFigures can measure it for free in your browser. On a PDF it sets the scale from the printed dimensions; on an image or photo, click both ends of a known length. Shift+A traces the building outline and leaves out the garage and porch, and the totals follow ANSI Z765-style rules. The Compare tab puts your measured figure next to the listed or county size, with the difference, the percentage and the price per square foot. Nothing is uploaded.
Questions
- How do I verify the square footage of a house?
- Compare the listing figure with the county property record card and any prior appraisal, then measure the house yourself: the outside walls at floor level, level by level, leaving out the garage and porches and keeping below-grade space separate. If your measurement and an ANSI Z765 appraisal agree, that's the number. If a gap remains that no single space explains, have an appraiser measure.
- Is the county's square footage accurate?
- It may be, but don't assume it. Assessors use their own local methods, may have recorded the house from plans or permits, and may not have updated the record after an addition, a finished basement or a garage conversion. Some include finished below-grade space in living area and some don't. Treat it as a cross-check, not a measurement standard.
- Should I measure square footage from the inside or the outside?
- From the outside for the home's total. ANSI Z765, the US standard for single-family homes, measures each level at floor level to the exterior finished surface of the outside walls. Interior measurements leave out the walls and give a smaller number. For an upper floor you can't reach from outside, measure inside and add the wall thickness, which you can measure at a door or window opening.
- When should I hire an appraiser to measure a house?
- When the number will decide something: a price negotiation, a property tax appeal or a dispute over a listing. Also when the house is hard to measure, with partly below-grade levels, sloped ceilings, a room over the garage or several additions. Ask for the measurement to follow ANSI Z765-2021 with above-grade and below-grade area reported separately.
- Does the appraisal square footage override the listing?
- Not formally, since there is no single legal standard for listings, but an appraisal measured by ANSI Z765-2021 is usually the more reliable figure because the method is published and the appraiser measured the house. Compare the appraisal's above-grade and below-grade figures with the listing; a finished basement included in the listing total is the most common reason they differ.