Home Buying
Zillow has its Zestimate, Redfin and Homes.com have their own value estimates, plus there are listing prices, selling prices, and tax assessments to appraisals. What should you believe?
If you’re in the market for a new home or selling your own, you’re probably using the internet to help. Prospective sellers ritualistically check home values online – especially their own — with many refreshing real estate apps as if they were day traders following a stock.
But as you browse listings and get a feel for what different homes may be worth, the numbers can get confusing. Zillow has its Zestimate, Redfin and Homes.com have their own value estimates, plus there are other estimates of value, from listing prices, selling prices, and tax assessments to appraisals. So, which should you believe?
“Understanding what goes into each home value estimate is really important,” said Bridget Frey, chief technology officer at Redfin. “People should use multiple sources to get an estimate for their home, including talking to a human real estate agent.”
Indeed, an agent understands the local market and can incorporate subjective factors into an otherwise objective valuation. For example, two homes may look similar on the outside, but a local agent who has toured them will know whether one’s been updated or if the owner is facing pressure to sell. Both factor into the value of a home, but the value estimates online may not reflect them.
Zillow’s Zestimate is perhaps the best known of the online home value estimates and, according to Zillow’s website, “incorporates public records, MLS data and user-submitted home details into Zillow’s proprietary home valuation model.” A Zestimate is not an appraisal, which is an unbiased estimate of a property’s value based on an exhaustive examination of comparable sales by a professional appraiser.
How accurate is a Zillow Zestimate? On its website, Zillow states that the nationwide median error rate is 1.77 percent for homes that are on the market and 7.20 percent for off-market homes. This means that “for homes currently listed for sale, the Zestimate is within 1.77 percent of the final sale price half of the time,” Zillow says.
But what about the other half? “It could be 100 percent off,” said Jonathan Miller, director of markets for StreetMatrix, a provider of hyper-local housing data and analytics for the financial sector and a state-certified real estate appraiser in New York and Connecticut. “The problem is that you, as a consumer, don’t know whether it’s within the 50 percent or not. So, while it’s a fun thing to play with, it’s not a reliable tool.”
In Greater Boston, Zillow’s median error is 2 percent, slightly higher than the national median, with 84.9 percent of Zestimates falling within 5 percent of the final sales price. Andy Krause, Zillow’s director of applied science, said the error rate is higher in Greater Boston largely because of the heterogeneity of the housing stock. The fact that the data comes from multiple sources, since the Boston metropolitan area includes several counties in Massachusetts, as well as parts of New Hampshire, plays a role in the error rate as well.
Steve McKenna, a real estate agent at Gibson Sotheby’s International Realty in Arlington, educates his sellers to help them arrive at a listing price for their homes. In the comparative market analyses he prepares, he includes not only his own opinion of value, but also the value estimates set by Zillow, Redfin, Homes.com, and local tax assessments.
“Every seller loves their home,” he said. “My goal is to take bias out of the equation and show them the realities of the marketplace.”
Even then, McKenna said, the ultimate value of a home depends on emotional, subjective factors and how badly a buyer wants it.
“Buyers should rely on their instincts,” he said. “First, get educated and understand market trends. But buying a home is a personal emotional decision, and Redfin or Zillow can’t tell you what a home is worth to you. Only you can decide that.”
How much are these homes actually worth?
9 Bonad Road, Arlington, Mass.
Redfin estimate: $1,508,013
Zillow estimate: $1,714,700
Homes.com estimate: $1,471,492
Tax Assessment: $1,446,200
List Price: $1,769,000
Sale Price: $2,019,000
Sale Date: Aug. 18, 2026
“A beautifully renovated Arts and Crafts bungalow located just a short distance from Menotomy Rocks Park. The home was tastefully restored, with its thoughtful renovations and original charm creating tremendous appeal among buyers. The property attracted multiple offers,” said Steve McKenna, a broker with Gibson Sotheby’s International Realty.
27 Park Circle, Arlington, Mass.
Redfin estimate: $1,412,729
Zillow estimate: $1,150,500
Homes.com estimate: $1,211,000
Tax Assessment: $1,224,300
List Price: $1,349,000
Sale Price: $1,475,000
Sale Date: July 9, 2026
“A charming and spacious Cape-style home ideally located near Robbins Farm Park and Brackett Elementary School. The property featured a generous yard and was meticulously maintained throughout. Its desirable location and welcoming character attracted strong buyer interest, resulting in multiple offers,” said Steve McKenna, a broker with Gibson Sotheby’s International Realty.
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