In real estate, fair market value (FMV) is the determined price for which a property will sell in an open market. The FMV is determined by a willing buyer and seller who are both reasonably knowledgeable about the property in question. To determine what fair market value is, you should begin with what it isn’t: fair market value isn’t what you (the buyer or seller) think the worth is. It’s not always the appraised price, and it’s not always the tax value.