What Is Comparable Sale?
Finding good comps means identifying 3-6 recently sold properties that closely match your subject in location (within 0.5-1 mile), recency (sold within 6 months), size (within 15-20%), and type (same property class). You then adjust each comp's sale price for differences -- adding value for features the comp lacks and subtracting for features the subject lacks. The adjusted prices form a range that indicates your property's market value.
A comparable sale (or "comp") is a recently sold property with similar characteristics to a subject property, used to estimate the subject's fair market value through the sales comparison approach -- the most widely used valuation method in residential real estate.
At a Glance
- Ideal Proximity: Within 0.5-1 mile of the subject property, same neighborhood or subdivision preferred
- Recency: Sold within 3-6 months (up to 12 months in slow markets)
- Size Match: Within 15-20% of the subject's gross living area
- Minimum Comps: 3 required for most appraisals; 5-6 preferred for investor analysis
- Data Sources: MLS, county recorder records, CoStar, PropStream, Zillow (verify independently)
- Primary Users: Appraisers, investors, agents, lenders
- Fannie Mae Guidelines: Require minimum 3 closed comps within 12 months
How It Works
Selecting Comparable Properties. The best comps share the most DNA with your subject property. Start with the tightest criteria: same subdivision, same floor plan, sold within 90 days. If you cannot find 3 matches, expand the radius to 1 mile and the time frame to 6 months. For rural or unique properties, you may need to go to 3 miles and 12 months. Fannie Mae guidelines require at least one comp from the same neighborhood and all comps within 12 months, though recent sales carry more weight.
Making Adjustments. No two properties are identical, so adjustments bridge the gaps. If your subject has 3 bedrooms and a comp has 4, you subtract the market value of that extra bedroom from the comp's price (typically $5,000-$15,000 depending on the market). If your subject has a renovated kitchen and the comp does not, you add the value of that improvement to the comp. Common adjustment categories include: gross living area ($50-$150/sq ft depending on market), bedroom count, bathroom count, garage spaces, lot size, condition, age, and upgrades. Adjustments should be market-derived -- based on how buyers actually pay for differences, not on improvement cost.
The Adjustment Rule of Thumb. Appraisers follow a guideline that no single adjustment should exceed 10% of the comp's sale price, and total net adjustments should stay under 15%. If you need adjustments exceeding 25% of the comp's value, it is not a good comp -- find a better one. Large adjustments introduce uncertainty that undermines the valuation.
Reconciling the Value. After adjusting all comps, you have a range of indicated values. The final value opinion leans most heavily on the comp requiring the fewest and smallest adjustments, as it is the most similar to the subject. If three adjusted comps indicate $325,000, $332,000, and $340,000, the value opinion will likely fall between $328,000-$335,000, weighted toward the most reliable comp.
Real-World Example
You are analyzing a 3-bedroom, 2-bathroom, 1,500 sq ft single-family home in a suburban Phoenix neighborhood, built in 2005, with a 2-car garage and no pool. You pull three comps:
Comp 1: 3/2, 1,620 sq ft, sold 45 days ago for $385,000, same subdivision, has a pool. Adjustments: -$12,000 (120 extra sq ft at $100/ft), -$18,000 (pool subject lacks). Adjusted price: $355,000.
Comp 2: 3/2, 1,480 sq ft, sold 60 days ago for $342,000, 0.4 miles away, no pool, needs cosmetic updates. Adjustments: +$2,000 (20 fewer sq ft), +$8,000 (inferior condition). Adjusted price: $352,000.
Comp 3: 4/2, 1,550 sq ft, sold 90 days ago for $368,000, 0.7 miles away, no pool, similar condition. Adjustments: -$10,000 (extra bedroom), -$5,000 (50 extra sq ft). Adjusted price: $353,000.
Adjusted range: $352,000-$355,000. Estimated fair market value: $353,000. Comp 2 required the smallest adjustments and gets the most weight.
Pros & Cons
- Most intuitive valuation method -- based on what buyers actually pay in the open market
- Widely accepted by lenders, appraisers, courts, and the IRS
- Effective in active markets with sufficient transaction volume
- Identifies specific value drivers (renovations, lot size, location) through adjustment analysis
- Allows investors to quickly estimate ARV for flip or BRRRR strategies
- Multiple data sources available (MLS, public records, commercial databases)
- Requires sufficient recent sales -- unreliable in low-volume or rural markets
- Adjustments involve subjective judgment, leading to different conclusions from different analysts
- Does not account for income-producing potential (use the income approach for rental properties)
- Comps reflect past transactions, not current market direction -- can lag in rapidly changing markets
- Unique or custom properties (lakefront estates, historic homes) may have no true comparables
- Off-market or distressed sales (foreclosures, estate sales) can skew comp data
Watch Out
- Cherry-Picking Comps. Agents and sellers often select the highest comps to justify a listing price. Always pull your own comps independently. Use the same search criteria consistently to avoid confirmation bias.
- Distressed Sales in the Mix. Foreclosure and short sale comps typically sell 10-20% below market. Include them only if the market has a high volume of distressed sales, and adjust accordingly.
- Stale Data. In a rapidly appreciating market (5%+ annually), a 9-month-old comp may understate value by 3-4%. Apply a time adjustment of the market appreciation rate per month.
- Square Footage Discrepancies. County records often differ from MLS listings. Verify GLA (gross living area) from the original appraisal or by measuring. A 200 sq ft error at $100/ft means a $20,000 valuation swing.
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The Takeaway
Comparable Sale is a practical deal evaluation concept that every serious investor should understand before committing capital. Whether you are buying your first rental property or scaling a portfolio, properly accounting for comparable sale helps you project returns more accurately and avoid costly mistakes. Master this concept as part of the deal analysis approach and you will make better-informed investment decisions.