Comp Adjustments: A Practical Guide
No two properties are identical. Even in a cookie-cutter subdivision, you'll find differences in square footage, lot size, upgrades, and condition. Comp adjustments bridge the gap between your subject property and the comparables you're using to estimate its value. Get them right, and your ARV is reliable. Get them wrong, and your entire deal analysis falls apart.
This guide explains how professional appraisers and experienced investors make comp adjustments, with real dollar ranges you can apply to your own analyses.
How adjustments work
The concept is simple. If a comp has a feature your subject property lacks, you subtract value from the comp's sale price. If the comp is missing a feature your subject has, you add value to the comp's sale price. You're adjusting the comp to make it more like the subject, not the other way around.
Rule of thumb: You always adjust the comp, never the subject. If the comp has a pool and the subject doesn't, subtract the pool value from the comp's sale price.
The adjusted comp prices should converge toward a narrow range. If your three comps sold for $280K, $295K, and $310K and after adjustments they land at $288K, $291K, and $294K, you have a tight cluster that gives you confidence in a $290K-$295K ARV. If after adjustments they land at $250K, $295K, and $340K, your comps aren't similar enough or your adjustments need work.
Square footage adjustments
Square footage is usually the largest single adjustment. The key is using the right per-square-foot rate for your market and price range.
For most markets in the $150K-$400K range, adjustments of $30-$80 per square foot are typical. In higher-priced markets, this can reach $100-$200+. The important thing is that the adjustment rate should be derived from your market, not from a national average.
To calculate your local adjustment rate, find two similar properties in the same neighborhood that sold recently where the primary difference is square footage. Divide the price difference by the square footage difference. Do this across several pairs and you'll see a consistent range.
Example: Comp A (1,800 sq ft) sold for $270K. Comp B (2,100 sq ft) sold for $291K. Same neighborhood, similar condition. Adjustment rate: ($291K - $270K) / (2,100 - 1,800) = $70/sq ft.
Be careful with large square footage differences. Adjustments become less reliable when the comp is more than 20-25% different in size from the subject. A 1,500 sq ft comp isn't a good match for a 2,500 sq ft subject even with adjustments.
Bedroom and bathroom adjustments
Bedrooms and bathrooms have diminishing marginal value. The jump from 2 bedrooms to 3 is significant (often $10K-$25K). The jump from 4 to 5 is much smaller (often $3K-$8K) because most buyers don't need more than 4 bedrooms.
Typical adjustment ranges for most markets ($150K-$400K):
- Bedroom: $5,000-$15,000 per bedroom (higher in family-oriented suburbs)
- Full bathroom: $8,000-$20,000 per full bath
- Half bathroom: $3,000-$8,000 per half bath
- Master suite (en-suite bath): $15,000-$25,000 premium over bedroom without bath
The key nuance: bedroom count matters most when it crosses common buyer thresholds. Going from 2 to 3 bedrooms opens the property to families and dramatically increases the buyer pool. Going from 5 to 6 doesn't change the buyer pool much.
Garage adjustments
Garage value depends heavily on local norms. In markets where most homes have 2-car garages, the adjustment for having one versus two can be $15K-$30K. In markets where street parking is common and garages are a luxury, a single garage might add $25K-$40K.
- No garage to 1-car: $10,000-$20,000
- 1-car to 2-car: $15,000-$30,000
- 2-car to 3-car: $8,000-$20,000
- Attached vs detached: Attached typically worth $3,000-$8,000 more
Lot size adjustments
In subdivisions with similar lot sizes (0.15-0.30 acres), lot adjustments are minimal. But when lots vary significantly, adjustments matter. Corner lots, cul-de-sac lots, and lots backing to green space command premiums.
- Standard lot size variance: $1,000-$3,000 per 1,000 sq ft in subdivisions
- Corner lot premium: $3,000-$8,000 (can be negative if on a busy road)
- Cul-de-sac premium: $5,000-$15,000
- Backing to greenbelt/park: $10,000-$30,000
- Waterfront or water view: 15-50% premium (highly market-dependent)
For rural properties with significant acreage differences, see our guide on how to comp rural properties.
Condition and update adjustments
Condition is subjective, which makes it the hardest adjustment to get right. Appraisers typically use a rating scale:
- C1-C2: New or like-new construction
- C3: Well-maintained, updated within the last 10 years
- C4: Average condition, showing some wear, may need cosmetic updates
- C5: Clearly deferred maintenance, needs renovation
- C6: Major repairs needed, distressed condition
The adjustment between each condition level varies by market but typically ranges from $5,000-$20,000 per level for homes in the $150K-$300K range. Moving from C5 to C3 (two levels) might warrant a $20K-$40K adjustment.
Specific update adjustments when the comp differs from your subject's post-renovation condition:
- Updated kitchen: $15,000-$40,000
- Updated bathrooms: $8,000-$20,000 each
- New flooring throughout: $5,000-$15,000
- New roof: $5,000-$12,000 (buyers expect it to be functional)
- New HVAC: $3,000-$8,000
Use the repair estimation tool to get accurate renovation costs that inform your condition adjustments.
Age adjustments
Year built matters less than you might think, as long as the homes are in similar condition. A well-maintained 1990 home can comp against a 2005 home with appropriate adjustments. The adjustment is typically $500-$2,000 per year of age difference, but it flattens out quickly. A 1970 home versus a 1975 home needs virtually no age adjustment. A 2000 home versus a 2020 home might need $10K-$20K.
The real age-related adjustment is for building code compliance. Homes built before certain code changes may lack features (arc-fault breakers, tempered glass, seismic strapping) that modern homes include. This is a functional obsolescence adjustment, not a pure age adjustment.
Location adjustments within the same market
Even within the same zip code, location differences can affect value. Properties on busy roads, near commercial zones, or adjacent to power lines typically sell for less than comparable properties on quiet residential streets.
- Busy road: -$5,000 to -$20,000 depending on traffic volume
- Near commercial/industrial: -$5,000 to -$15,000
- Power line proximity: -$5,000 to -$15,000
- Near school or park: +$3,000 to +$10,000
- Flood zone: -$10,000 to -$30,000+ (plus insurance cost impact)
The maximum adjustment rule
Appraisers follow a general guideline: no single line-item adjustment should exceed 10% of the comp's sale price, and total net adjustments shouldn't exceed 15-25%. If you're adjusting a comp by more than 25%, it's probably not a good comp.
If total adjustments exceed 15-25% of the comp's sale price, find a better comp.
This rule exists because each adjustment introduces estimation error. The more adjustments you stack, the more error accumulates. Three small adjustments of $5K each are more reliable than one large adjustment of $15K.
Paired sales analysis
The most accurate way to derive adjustment values is through paired sales analysis. Find two properties that sold recently in the same area where the primary difference between them is the feature you're trying to value. The price difference between the two sales is your adjustment value.
This works well for binary features (pool vs no pool, garage vs no garage). It's harder for continuous variables (square footage, lot size) but still useful when you can find good pairs.
Deal Run's comp analysis makes paired sales analysis easier by letting you filter and sort comps by specific characteristics, so you can quickly identify pairs that isolate individual features.
Putting it all together
Here's a practical example. Your subject property after renovation will be a 3-bed/2-bath, 1,600 sq ft home with a 2-car garage on a 0.20-acre lot in good condition.
Comp A: 3/2, 1,850 sq ft, 2-car garage, 0.22 acres, good condition, sold for $285,000.
- Square footage: (1,600 - 1,850) x $65/sq ft = -$16,250
- Lot size: negligible difference
- Adjusted value: $285,000 - $16,250 = $268,750
Comp B: 4/2, 1,550 sq ft, 2-car garage, 0.18 acres, good condition, sold for $272,000.
- Square footage: (1,600 - 1,550) x $65/sq ft = +$3,250
- Bedroom: (3 - 4 bedrooms) = +$10,000
- Adjusted value: $272,000 + $3,250 + $10,000 = $285,250
Comp C: 3/2, 1,620 sq ft, 1-car garage, 0.19 acres, average condition, sold for $248,000.
- Square footage: negligible difference
- Garage: (2-car - 1-car) = +$20,000
- Condition: (good - average) = +$12,000
- Adjusted value: $248,000 + $20,000 + $12,000 = $280,000
Adjusted range: $268,750 to $285,250. A reasonable ARV estimate would be $275K-$280K, weighting the most similar comp (C, with minimal size adjustment) slightly higher.
Use the ARV calculator to run these adjustments systematically for any property.
Related articles
- How to Calculate ARV Step by Step
- How to Run Comps Like a Pro
- How to Comp Rural Properties
- ARV Mistakes That Kill Deals