How to Comp a House: A Practical Guide to Real Estate Comps

Across 2,235 US markets with at least 100 tracked sales, the middle half of homes sell inside a band that spans 34 percent of the market's own median price per square foot. In Chicago that band runs from $172 to $375. Picking the wrong half of it is not a rounding error, it is the whole deal.

Comping, short for running comparable sales, is the work of deciding which of those sales describe your property and which do not. Every valuation downstream, an offer, an after repair value, a listing price, an assignment fee, rests on that choice. This is how to do it, and where it usually goes wrong.

What a comparable sale actually is

A comp is a property that has closed, recently, near yours, that a buyer would have considered instead of yours. All four parts carry weight:

• •Closed, not listed. An asking price is a hope. A closing is a fact, agreed by a buyer, a seller, a lender and an appraiser. Active listings tell you about competition, not value.
• •Recent. Six months is the working standard. Twelve is the outer limit, and in a market that has moved sharply a year-old sale describes a different market rather than a different house.
• •Near. A mile is a reasonable radius in a suburb. In a dense city, values change street to street, so a few blocks is the honest limit. School attendance boundaries and water frontage can flip value across a road.
• •Similar, and similarly finished. Same property type, square footage within roughly 20 percent, same bedroom and bathroom count, comparable lot, and finished to the standard yours is in or will be in.

How much the spread varies by market

Comp selection matters more in some places than others, and the difference is measurable. Using closings Resideline tracked over the twelve months to 17 August 2026, here is the middle half of the price per square foot in six of the largest markets:

In Las Vegas the middle half spans only 31 percent of the median, so a sloppy comp costs you a little. In Philadelphia it spans 83 percent, and the same sloppiness costs you the margin. A quarter of all measured markets sit above 43 percent.

The process, start to finish

1. Define the subject honestly. Square footage above grade, bedrooms, bathrooms, lot size, year built, garage, and the condition today. Write down the finish level you are comparing to, because that decides whether you want renovated comps or tired ones.

2. Pull a wide net, then cut. Start with sales in the last six months within a mile. If that gives you fewer than six candidates, widen the radius before you widen the date range. Time moves value more predictably than geography does.

3. Cut to three to five. More is not better. Three genuinely similar closings beat ten loose ones, because every weak comp you keep drags the estimate toward the middle of the market rather than toward your property.

4. Adjust, and write the adjustments down. A comp with an extra bathroom, a finished basement or 300 more square feet is not the same house. Adjust for the difference, note the figure, and keep the note. If you cannot defend an adjustment to a lender or a buyer, do not make it.

5. Reconcile, do not average. Weight the closest match highest. A median across your final set is safer than a mean, because one unusual sale moves a mean a long way.

A worked example

A 1,400 square foot three bedroom, two bathroom house, built 1994, needs a full cosmetic renovation. Within half a mile, four renovated homes of similar size closed in the last five months at 238, 252, 261 and 249 dollars per square foot. The median is 250.

• •After repair value: 1,400 x 250 = 350,000 dollars
• •One comp had a finished basement and sold at 261. Excluded rather than adjusted, because the adjustment would have been a guess.
• •The remaining three give a median of 249, which rounds to the same answer. That agreement is the signal that the set is sound.

Run the same numbers yourself in the ARV calculator, then screen the deal with the 70 percent rule calculator.

Where comping goes wrong

• •Using listings. The most common error, and it inflates everything downstream.
• •Ignoring finish level. Two identical floor plans can differ by 30 percent on finish alone.
• •Crossing an invisible line. A school boundary, a flood zone, a rail line or a city limit can change value more than a mile of distance.
• •Averaging everything you found. The mean of ten comps is a description of the neighborhood, not of your house.
• •Keeping a comp because it helps. If you would not defend it to a buyer, it is not evidence.
• •Comping from the price per square foot alone. It carries no information about the lot, the road, the layout or the roof.

Comping for different jobs

• •For an offer on a rental , comp the as-is condition. You are buying what is there today.
• •For an after repair value , comp renovated homes only, at the finish level you intend to deliver.
• •For a listing price , comp both, because the gap between them tells you what the renovation is worth to this particular buyer pool.
• •For a wholesale assignment , comp the way your end buyer will, because their number is the one that closes the deal.

Where to get the sales

You need closings, and public portals mostly show listings. Resideline's ZIP market snapshots publish the median closed price and price per square foot for every ZIP with enough sales to be read honestly, which is the fastest way to sanity check a figure before you spend time on a property. A full property report returns the individual comparable sales behind a value, with the adjustments shown.

Figures in this article come from closings Resideline tracked over the twelve months to 17 August 2026, covering 2,235 markets with at least 100 sales each. Updated September 11, 2026.