CMA vs appraisal vs online estimate
Three numbers, three different jobs. Sellers routinely treat them as competing opinions of the same thing, which is why the conversation goes wrong before it starts.
The short version
| CMA | Appraisal | Online estimate | |
|---|---|---|---|
| Who produces it | A licensed agent | A licensed or certified appraiser | Software, unassisted |
| Question it answers | What should we list at? | What is it worth, for a lender? | Roughly what range is this in? |
| Property inspected | Usually, by the agent | Yes, to a defined standard | Never |
| Adjustments | Agent's judgment, shown | Formal, documented, defensible | Statistical, not disclosed |
| Used for lending | No | Yes | No |
What a CMA actually is
A comparative market analysis is an agent's pricing recommendation, supported by recent comparable sales adjusted to the subject property. It is prepared to answer a commercial question — what price will get this house sold, in this market, in the time the seller has — and it draws on things no model sees: that the kitchen was redone last year, that the house backs onto a road, that two similar homes went under contract in a weekend.
It is not a formal opinion of value, it is not prepared to appraisal standards, and no lender will accept it in place of one. That limitation is not a weakness; it is a different job.
What an appraisal is
An appraisal is a formal opinion of value prepared by a licensed or certified appraiser, usually for a lender deciding how much to lend against the property. Appraisers work to professional standards, inspect the property, document their comparable selection and adjustments, and are accountable for the result.
It is the number that governs when a mortgage is involved. When an appraisal comes in below the contract price, that is the number the deal has to survive — which is exactly when a well-documented CMA earns its keep, because it is the evidence an agent uses to make the case for reconsideration.
What an online estimate is
Automated valuation models — the estimate on a portal listing, of which Zillow's Zestimate is the best known — apply a statistical model to public records and prior sales. They are genuinely useful as a starting range and genuinely misleading as a conclusion, because the model cannot see condition, finish, layout, or anything about the property that has not been recorded.
Their published accuracy is a median across enormous volumes of homes, which means half of all estimates are further off than the headline figure, and the misses cluster exactly where you would expect: unusual homes, thin markets, and anywhere a property has changed materially since the last recorded sale.
An AVM is a reasonable input to a CMA. It is not a substitute for one, and the difference is worth explaining to a seller before they quote one at you.
Answering the seller who arrives with a Zestimate
Do not argue with the number. Explain what produced it: a model, working from recorded data, that has never seen the house. Then show them the sales you chose, why each one is comparable, and what you adjusted. A seller who understands that their estimate came from a computer that does not know about the new roof will usually price it themselves, correctly, in the next five minutes.
That conversation goes better with the evidence in front of you, which is the argument for producing a real CMA for every listing appointment rather than only the ones you expect to be difficult. The method is here, and CompAgent does the assembly in about a minute so producing one is never the reason you skipped it.