Home value basics
How home value estimates work — and how accurate they are
Online home value tools all work roughly the same way, but estimates can still vary meaningfully between providers. Here's what actually goes into the number, why it moves between sites, and when it's worth getting a local professional's opinion instead.
What goes into an estimate
Most home value tools start with public property records: square footage, lot size, bedroom and bathroom count, year built, and past sale price. They then compare that against similar homes nearby that have sold recently, adjusting for differences in size, age, and location to arrive at an estimated range.
Why estimates differ between websites
Two tools looking at the same address can produce different numbers because they pull from different data sources, use different sets of comparable sales, and weigh factors differently. Neither number is necessarily "wrong." They're different models making different assumptions from overlapping but non-identical data.
What most tools can't see: interior condition, recent renovations, and finish quality generally aren't reflected in an automated estimate unless that information has been manually entered. Two homes with identical square footage on the same block can have very different real market values for reasons an algorithm has no way to know.
Estimate vs. appraisal vs. agent opinion
- Online estimate: a computer-generated approximation based on public data and comparable sales. Fast, free, and a reasonable starting point.
- Appraisal: an in-person inspection by a licensed appraiser, used by lenders to underwrite a mortgage. Considered authoritative, but not free and not typically obtained just out of curiosity.
- Agent comparative market analysis (CMA): a local agent's assessment based on recent comparable sales plus their knowledge of your specific home and neighborhood. Often free, and generally more tailored than an automated estimate.
How accurate is "accurate" here?
Accuracy depends heavily on how much recent, comparable sales data exists nearby. In a neighborhood with lots of recent, similar home sales, estimates tend to track closely to eventual sale prices. In areas with few recent transactions, unique properties, or rapidly shifting markets, the estimate is a rougher approximation. That's why most reputable tools present a range rather than a single confident number.
When to get a local professional's opinion
An online estimate is a fine starting point for general curiosity. Before setting an asking price, listing a home, or making a decision that depends on an accurate number, it's worth getting a local agent's opinion. They can account for your home's actual condition, recent upgrades, and hyper-local market conditions in a way an automated tool simply can't.
Frequently asked questions
How do online home value estimators calculate a value?
They start with public records (square footage, lot size, bedrooms/bathrooms, past sale price) and compare a home to similar nearby properties that have sold recently, adjusting for differences in size, condition, and location.
Why do home value estimates differ between websites?
Different tools use different data sources, different comparable sales, and different algorithms, so estimates for the same home can reasonably vary between providers. None account for interior condition or recent renovations unless manually added.
Is an online home value estimate the same as an appraisal?
No. An appraisal is performed in person by a licensed appraiser and used by lenders to underwrite a mortgage. An online estimate is a computer-generated approximation meant as a starting point, not a substitute for a professional appraisal or an agent's market analysis.
How accurate are home value estimates?
Accuracy varies by market and by how much recent comparable sales data is available. It's more reliable in areas with lots of recent, similar sales, and less reliable for unique properties or areas with few recent transactions. Most providers present a range rather than a single number for this reason.
When should I get a real estate agent's opinion instead of an online estimate?
Before listing a home for sale, before setting an asking price, or whenever a property has features an algorithm can't see. A local agent's comparative market analysis accounts for factors online tools miss.
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Get Free Home ValueGeneral educational information, not financial, legal, or appraisal advice. For a binding valuation, consult a licensed appraiser; for a market-specific opinion, request a comparative market analysis from a local agent. Last reviewed August 2026.