This site can be helpful, if you ignore the "Zestimates" and expect a lot of out-of-date listings. The Zestimate for my listing was about 30% high. Then it dropped suddenly by about 60%, and eventually sold for a price nowhere near ether figure. It's still listed on Zillow although it was sold almost two months ago. Instructions for removing the listing don't work. Neither do the instructions for reporting a problem. The mapped location for the address was about two miles off in the middle of a cranberry marsh.