Square Footage Adjustment Calculator
This calculator provides a rule-of-thumb estimate for comparative market analysis in the Reno–Sparks area. It is not an appraisal and should not be relied upon as a formal opinion of value. Adjustments should always be reviewed in the context of the full comparable data set.
Time Adjustment Calculator
Market-conditions adjustment for comparable sales, indexed to the Reno–Sparks single-family median by quarter, Q1 2020 – Q2 2026.
Median Sales Price by Quarter — Reference Table
| Quarter | Median Sales Price |
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Comparable adjustment
Garage
Enter a comparable sale and its garage count. The tool returns the dollar adjustment to apply to that comp so it matches a subject property with the opposite garage count.
Closed price of the comp, not the list price.
Subject is treated as 3-car.
Adjustment to the comparable
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Enter a sale price to calculate.
How this number is derived
Built from 9,509 Reno/Sparks closed sales, January 2025 through July 2026. The premium is the coefficient on garage count in a regression of log sale price that holds living area, lot size, age, bedrooms, bathrooms, stories, month of sale and elementary school zone constant. Pooled across the whole range it is 3.7%; estimated within five price tiers it averages 2.9%.
Those tier-by-tier estimates were too noisy to use as a step schedule — a formal test found no significant variation between them, and the apparent differences fell inside the margin of error. Forcing them into brackets produced large jumps at arbitrary price points. This version replaces them with one continuous curve fitted through the tier estimates, weighted by the precision of each.
The curve is adjustment = $18,000 × √(price ÷ $600,000), anchored at 3.0% of $600,000 where the data is densest. Square-root scaling treats a garage bay as partly a fixed cost and partly proportional to value, which is why the percentage eases as price rises while the dollar figure keeps climbing. It fits the tier estimates as well as any other exponent tested (weighted χ² 5.73 versus 5.68 for the best-fitting one).
Above roughly $850,000 the underlying estimates thin out: 74% of homes in that range already have three bays, leaving little contrast to measure. The curve still returns a figure there and flags it. Consider adjusting for the absence of a third bay instead.
Single-family only. Not calibrated for condos, townhouses or manufactured homes, or for garages of one, four or more bays.
Comparable adjustment
Lot size
Enter both lot sizes and the zip code. The tool returns the dollar adjustment to apply to the comparable so its lot matches the subject.
Pre-filled with the zip's median sale price. Overwrite with the actual comp.
Adjustment to the comparable
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Enter both lot sizes to calculate.
- Lot elasticity
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- Value of +0.01 ac
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- Sales in model
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How this number is derived
Built from 7,605 single-family closed sales in Washoe County, January 2025 through July 2026. Within each zip code, sale price is regressed on lot size, holding living area, age, bedrooms and bathrooms constant, so the lot coefficient measures land rather than the house standing on it.
Both sides of that regression are logged, which makes the coefficient an elasticity: in 89521 it is 0.173, meaning a lot 1% larger sells for 0.17% more. The adjustment applies it directly — comp price × [(subject acres ÷ comp acres)b − 1] — rather than multiplying a flat rate by the acreage difference.
That matters because land value is not linear. An extra 0.01 acre is worth far more on a 0.10-acre lot than on a one-acre lot, and a straight-line rate would badly overstate large-lot adjustments. The "value of +0.01 ac" figure shown above is the slope at the comparable's own lot size, not a fixed rate for the zip.
Zips with fewer than 40 sales — 89501, 89510 and 89705 — fall back to the market-wide elasticity of 0.132 and are flagged. Any pair of lots outside the middle 90% of that zip's observed range is also flagged, since the model is only calibrated across the sizes actually sold there.
Single-family only. Lot sizes below 0.02 acres and implausible outliers were excluded; note that some MLS records carry clerical errors in the lot field, so confirm unusual acreages against the parcel record.