How to run comps on a property
Running comps on a property is a five-step process: draw the search box before you look at any sales, pull every closed sale inside it, reject the ones that don't qualify, adjust the survivors for the differences that remain, then weight the closest matches most heavily and read off a value range rather than a single number. Done properly on one address it takes about twenty minutes and produces a figure you can defend line by line.
Draw the box before you look
Write down your radius, your date window, your square-footage band and your property type before you open a single sale. This costs thirty seconds and it is the only defense against the most natural failure in the whole process: seeing a number you like and constructing criteria that admit it.
A defensible default set of boundaries, and when to move them:
| Boundary | Default | Tighten when | Loosen when |
|---|---|---|---|
| Radius | 0.5 mi | Dense urban grid; value changes block to block | Rural; nothing closer has sold |
| Recency | 6 months | Prices are moving fast in either direction | Very low turnover; go to 12 and say so |
| Size band | ±20% | Small houses, where 20% is only 250 ft² | Large or unusual houses with few peers |
| Type / era | Exact match | Always — this one shouldn't flex | Never |
One boundary that never flexes: don't cross a school-attendance, municipal, or flood-zone line. Those move price by amounts you can't see in a photo and can't defend adjusting for.
Pull everything, then reject hard
Pull every closed sale inside the box — all of them, before filtering — because the ones you throw out tell you about the market too. A box that yields twenty sales in six months is a liquid neighborhood; one that yields four is a signal about your exit.
Then reject. Out go non-arm's-length transfers, foreclosures and REO, sales with heavy concessions, and anything carrying a feature your subject won't have. How to find real estate comps covers the full rejection list and where each source hides the evidence.
Adjust what's left
Adjustments run toward the subject: if the comp has something your property won't, subtract it from the comp's price; if yours will have something the comp lacked, add it. Work in dollars, not percentages, and keep a written line per adjustment.
The discipline that matters is restraint. A comp requiring three or more adjustments is not a comp — it is a different house you are arguing into the set. And if every adjustment in your table happens to push the value up, stop: you're not adjusting, you're advocating.
Run this on a real address
Faro does the pull, the rejection and the weighting for any US address, and shows the comparable sales it used on a map so you can check its work rather than take it on faith.
Weight, then quote a range
With three to six adjusted comps, take the median. That is your baseline and it needs no further defense. If your set genuinely varies in quality — one comp is on the subject's own street and two are a half-mile out — a simple weighting is worth applying on top.
Weights that hold up, and don't require a spreadsheet:
| Comp quality | Weight | What earns it |
|---|---|---|
| Strong | 3 | Same street or subdivision, sold within 90 days, no adjustments needed |
| Good | 2 | Inside the box, sold within 6 months, one modest adjustment |
| Weak | 1 | At the edge of the box, or two adjustments, or 6–12 months old |
Multiply each comp's adjusted price per foot by its weight, sum, divide by the total weight, and multiply by your square footage. Then — and this is the step almost everyone skips — write down the value implied by your weakest comp and by your strongest. That pair is your range.
Quote the range with the number, every time. "About $386,000, in a range of $349,000 to $405,000" is an honest statement about a five-comp set. "$385,600" on its own implies a precision the data does not contain, and it is the sentence people talk themselves into deals with.
What the number is for
A completed comp run feeds three different decisions, and it is worth being clear which one you're making. Against an asking price, it tells you whether the listing is over, under, or fairly priced — the starting point for finding underpriced homes. Run on renovated comps instead, it becomes an ARV, which drives the maximum allowable offer. And on a rental, today's value is what every return figure is computed against.
Common questions
How long should running comps take?
About twenty minutes per property once you have a source and a routine, and most of it is rejection rather than analysis. If it is taking an hour, you are almost certainly adjusting comps you should be discarding.
What if there are no good comps?
Then say so, and act accordingly. A thin comp set is a real finding about the property — unusual houses and thin markets carry genuine liquidity risk, and the correct response is a wider quoted range and a lower offer, not a wider search radius until three sales appear.
Should I weight comps or just take the median?
Take the median first, always — it is the honest baseline and it needs no assumptions. Weighting is a refinement on top of it, and it is only worth doing when your set genuinely varies in quality. If weighting moves your answer more than about 3% off the median, check whether you're weighting toward similarity or toward the answer you wanted.
Do I run comps on the house as-is or as renovated?
Both, for a project — they answer different questions. As-is comps tell you what the property is worth today, which is what you're negotiating against. Renovated comps give you the ARV, which is what your exit depends on. ARV vs market value covers the gap between them.
Related guides and calculators
How to find real estate comps
Where the sold data actually lives, and the six filters that separate a comp from a nearby house.
How to calculate ARV
The five-step method, with a worked example and the adjustment table most investors skip.
How to analyze a wholesale deal
End-to-end on one property, including the buyer's-side check most wholesalers never run.
ARV vs market value
Two different numbers on the same house — where the gap comes from and who uses which.
Twenty minutes, or one address.
Faro runs the whole process for any property — the comp set, the weighting, the value, and the offer price that hits your return.
Estimates for analysis and educational use only — not financial, investment, tax, or legal advice. Verify every number independently before making a purchase decision.