What is a comp, and how do agents actually pick them?

Almost every home valuation, whether it comes from an agent, an appraiser, or a website, rests on comps. A comp, short for comparable sale, is a home similar to yours that recently sold, used as evidence for what yours is worth. Understanding how comps are chosen tells you more about pricing than any single number does.

What makes a home a genuine comp

A strong comp is close to your home on the things that actually drive price: location, size, bedroom and bathroom count, age, style, and condition, and it sold recently. Proximity matters because neighborhoods, and even blocks, carry different values. Recency matters because the market shifts month to month. A sale from the same street three months ago is worth far more as evidence than a similar house a mile away that sold last year.

Why the selection is the whole game

Here is the part most people miss. The same home can be made to look worth more or less depending on which comps you choose. Pick three high sales and the number climbs; pick three low ones and it falls. This is why comp selection is not a clerical step. It is the core judgment of the entire valuation, and it is where skill and honesty matter most.

Where automated estimates go wrong

An automated valuation selects comps by matching data fields: square footage, beds, baths, distance. It cannot see that one comp was a dated home sold as-is, or that another sold high because of concessions never recorded in the price, or that a third backs to a highway while yours backs to a park. It treats look-alike data as if it were a look-alike home. A good agent throws out the comps that do not truly belong and explains why, which is the judgment the software skips.

How to read a comp set yourself

When you see the comps behind a price, ask three things. Are they genuinely close in location and recent in time? Are they similar in condition, not just size? And is there a story behind any of them, a rushed sale, a renovation, a concession, that changes what the number means? A price is only as trustworthy as the comps under it.

Common questions

How many comps make a reliable valuation?

Three to five genuinely similar, recent sales is a solid basis. What matters is quality, not count: five true comparables beat a dozen loose ones. One or two, or older or dissimilar sales, produce a shaky number.

Why do two valuations use different comps?

Because comp selection is a judgment call. Two people can look at the same home and reasonably choose different comparables, which is exactly why the number moves. When valuations disagree, the difference is almost always in which comps each one trusted.

Can I choose comps that make my home look more valuable?

You can cherry-pick high sales, but it does not fool the market. Buyers and their agents run their own comps, and an appraiser will too. A price built on flattering but weak comps tends to sit unsold until it is corrected.

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Sources: Zillow Research on pricing and time on market; NAR pricing guidance, 2026; Realtor.com market data, 2026.

This is general information, not financial advice. A local agent can assess the specific comparable sales for your home.