You can look up a house value using free public records, but the number you find depends on which source you check
A house's value at a specific address is not a single fixed number. Tax assessors, real estate websites, and recent sales all produce different estimates, and they measure different things. A tax assessment is what your local government thinks the house is worth for property tax purposes. A Zillow estimate is based on an algorithm trained on recent sales in the area. The actual sale price from last month is a historical fact, not a prediction of what it's worth today.
The fastest way to find a value is to search the address on Zillow, Redfin, or Realtor.com. These sites show you an estimate (often called a "Zestimate" on Zillow), recent sale history, and sometimes property tax records all in one place. If you want the official tax assessment your local government uses, you search your county assessor's website directly—the process and website vary by county, but most assessors have a searchable database online.
Key Takeaways
- Tax assessments, online estimates, and recent sale prices are three different numbers that measure different things.
- Zillow, Redfin, and Realtor.com show estimates and recent sales history for free, though their estimates can be off by thousands of dollars.
- Your county assessor's website holds the official property tax assessment, which you can search by address at no cost.
- A professional appraisal ordered by a lender or buyer is the most accurate measure of value, but it costs money and is not public.
What tax assessments measure and where to find them
A property tax assessment is an estimate your county or municipality makes to decide how much property tax you owe. It is not the same as market value—it is often lower, and it updates on a schedule (every year, every three years, or every five years depending on your state). The assessment is public record and searchable by address on your county assessor's website.
To find it, go to your county's official website and look for "assessor," "property appraiser," or "property records." Type in the street address. The result will show you the assessed value, the lot size, the year built, the number of bedrooms and bathrooms, and sometimes recent sales of comparable properties nearby. Some counties also show the property tax bill itself, which is the assessed value multiplied by your local tax rate.
The assessed value is useful because it is official and consistent, but it lags behind the market. If your house sold for $400,000 last year and the market has risen 10 percent since then, the assessment might still show $350,000 because assessments do not update monthly.
How online estimates work and why they vary
Zillow, Redfin, Realtor.com, and similar sites use algorithms to estimate a house's value. They feed the algorithm recent sales of similar houses in the same neighborhood, the house's age and size, and other public data. The algorithm spits out a number. Zillow calls this the "Zestimate." Redfin calls it the "Redfin Estimate." The name changes, but the idea is the same: a computer-generated guess based on comparable sales.
These estimates are free and usually appear within seconds of you typing an address. They are also often wrong—sometimes by a little, sometimes by tens of thousands of dollars. The further a house is from recent sales of similar properties, the less reliable the estimate. A unique house in a rural area with few recent sales will have a less accurate estimate than a standard three-bedroom in a busy suburb where houses sell every month.
The estimates also change frequently. If a house nearby sells for more than expected, your estimate might jump up. If the market slows, it might drop. These swings do not mean the house's actual value changed—they mean the algorithm adjusted based on new data.
Recent sale prices and what they tell you
The most concrete number you can find is a recent sale price. If a house sold three months ago for $425,000, that is a fact. You can find recent sales on Zillow, Redfin, and Realtor.com by searching the address and scrolling to the "Zestimate" or "Price History" section. You can also search your county assessor's website, which often lists the most recent deed recording and sale price.
A recent sale price is useful because it is real, but it is also old information. A house that sold for $425,000 in January might be worth more or less in June depending on whether the market has moved. If you are trying to understand what a house is worth right now, a sale from six months ago is a starting point, not an answer.
Sale prices are also public record. When a deed is recorded at the county, the sale price is usually included and becomes searchable. Some counties hide the price, but most do not.
The difference between estimates and appraisals
An appraisal is a professional estimate ordered by a lender or buyer. A licensed appraiser visits the house, measures it, inspects it, and compares it to recent sales of similar properties. The appraisal is detailed and usually accurate, but it costs $300 to $500 and is not public record. Only the person who ordered it sees the result.
If you are buying a house, the lender will order an appraisal to make sure the house is worth what you are paying for it. If you are selling, the buyer's lender will order one. If you are a homeowner trying to understand your house's value for your own reasons, you would have to pay for an appraisal yourself—most people do not.
The appraisal is the most accurate measure of value because it is done by a human who knows the local market and can see the actual condition of the house. An online estimate is faster and free, but it cannot see inside the house or account for recent renovations or damage.
Why the same address shows different values on different websites
Zillow, Redfin, and Realtor.com use different algorithms and sometimes different data sources. One site might weight recent sales more heavily; another might factor in the condition of the house based on photos. One site might have access to a recent sale that another does not. The result is that the same address can show three different estimates.
This is normal and expected. None of them is "right"—they are all educated guesses. If Zillow says $450,000 and Redfin says $465,000, the true value is probably somewhere in that range, but it could be outside it. The wider the gap between sites, the less certain any of them are.
If you are trying to decide what to list a house for or what to offer on one, you should look at all three sites, check your county assessor's records, and look at recent sales of similar houses in the neighborhood yourself. The more sources you cross-check, the clearer the picture becomes.
What to do if you need an official value for a specific reason
If you need a value for insurance, a loan, or a legal dispute, you usually cannot use an online estimate. Insurance companies want an appraisal. Lenders want an appraisal. Courts want an appraisal or expert testimony. If you are contesting your property tax assessment, you can challenge it using comparable sales data, but the assessor's office will not accept a Zillow estimate as proof.
For property tax disputes, most counties allow you to file a formal challenge (called an appeal, a protest, or a reassessment request depending on your state) if you believe the assessed value is too high. You submit comparable sales data showing that similar houses sold for less. The assessor reviews it and either adjusts the value or denies the appeal. This process is free but takes time.
For insurance or lending purposes, you will need to hire a licensed appraiser. Your insurance agent or lender can recommend one, or you can search your state's appraiser licensing board online.
Frequently Asked Questions
Is the Zillow estimate the same as what my house is actually worth?
No. The Zillow estimate is a computer guess based on recent sales and public data. It can be off by thousands of dollars, especially for unique houses or in areas with few recent sales. It is a starting point, not a final answer. If you need to know the actual value for a financial decision, get a professional appraisal.
Can I use an online estimate to challenge my property tax assessment?
No. Tax assessors do not accept online estimates as evidence. If you want to challenge your assessment, you need to submit comparable sales data—actual recent sales of similar houses in your area. Your county assessor's office can tell you what documents they need and how to file a formal challenge.
Why does the value on Zillow keep changing?
Zillow updates its estimate whenever new sales data becomes available in your area. If a similar house sells for more than expected, your estimate might jump up. If the market slows, it might drop. These changes reflect new information, not changes to your actual house. The estimate is only as good as the recent sales data available.
How old can a sale price be before it is no longer useful?
A sale from the last three to six months is usually relevant. Beyond that, the market may have moved enough that the price is outdated. In a fast-moving market, even three months can be old. In a slow market, a year-old sale might still be useful. Check multiple recent sales, not just one.
Do I need an appraisal to sell my house?
No. You set the listing price yourself, usually with help from a real estate agent who analyzes comparable sales. The buyer's lender will order an appraisal to make sure the house is worth the purchase price. If the appraisal comes in low, the buyer may renegotiate or walk away.