The direct answer
Adjust a comparable sale to express what its price suggests for the subject after accounting for relevant differences. The direction and amount need support from evidence; the calculator accepts already adjusted values and does not derive market adjustments.
Create a difference inventory
Compare location, size, condition, sale timing and features that are relevant to the property’s market. Identify which differences are already reflected in another adjustment. A size adjustment and a price-per-square-foot scaling can overlap if applied carelessly. Do not automatically assign a dollar value to every visible difference; some features may have no supported separate market contribution.
To apply the approach to an editable scenario, use the Comparative Market Analysis (CMA) Calculator. For the neighboring question, explore Property Value Calculator.
Translate the comparable toward the subject
A comparable superior to the subject in a valued feature generally needs a downward adjustment when translating its price to the subject. An inferior comparable generally needs an upward adjustment on that feature. The amount must come from relevant market evidence rather than the construction cost or an arbitrary percentage. Keep signs and explanations visible in a working table before entering the resulting indication.
Reconcile the adjusted values without hiding uncertainty
Large adjustments can indicate weak comparability, even when the final numbers cluster. Custom weights may give more influence to more relevant evidence, but do not verify it. The CMA tool’s median and range summarize the entered adjusted values; they are not confidence intervals or formal appraisal conclusions. Review sensitivity to the adjustments instead of reporting only a precise-looking average.
Worked example
For an illustrative $515,000 sale with a supported $15,000 superior-feature adjustment, subtracting that amount gives a $500,000 subject indication. A second sale at $490,000 with a supported $10,000 inferior-feature adjustment also indicates $500,000. The matching arithmetic does not independently prove either adjustment.
Open Comparative Market Analysis (CMA) Calculator and test your assumptions →
Common mistakes and limitations
Do not add the cost of an improvement as its value contribution without supporting evidence. Do not apply an adjustment twice through separate size and feature calculations.
Does not access MLS and is not a licensed appraisal. Adjustments are supplied by the user.
Frequently asked questions
Does the calculator choose adjustment amounts?
No. Enter already adjusted comparable values supported by your evidence.
Do matching adjusted prices prove the estimate is correct?
No. Agreement can result from shared weak assumptions; review the selection and adjustment support.
Sources and further reading
The article’s examples are illustrative arithmetic. The references below provide context for operating, valuation or transaction concepts; they do not endorse the assumptions or the calculator.
- IRS — Instructions for Form 709 (2025) — real property valuationComparable-sales concept and adjusting for differences in date, size, condition and location.
- IRS — Publication 551 (12/2025), Basis of AssetsFair-market-value concept and use of similar-property sales as evidence.
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