Most families going through a divorce have to decide if they are going to sell the house or whether one person will buyout the interest of the other. If the house will be sold the answer is easy: whatever someone is willing to pay that is acceptable to both owners. This presumes that the offer is within a certain range of the listing price of the house.
If one person wants to keep the house and buy out the other person house the first option is to see if you both agree on the value of the house. If you don't agree, the least expensive option is for each of you separately or jointly to consult with a local real estate broker and obtain the broker's opinion. The broker may prepare a Comparative Market Analysis (CMA) which information comes from the Multiple Listing Service. The report is usually free because the broker hopes to generate a listing. The report details the general description of homes that are in the community that have either sold, are in contract or are listed for sale. By comparing home styles that are similar to your home, a general range of value can be estimated.
The more complete and accurate way to determine fair market value of the home is to hire a real estate appraiser. Unlike the real estate broker who usually does not visit the house, the appraiser will make an appointment and come to the house and look at the inside and outside and then after taking notes about the property, its location and condition of the house the appraiser will prepare a formal report that seeks to use recent sales in the neighborhood with adjustments made for the variations between the other properties and yours. The variations will take into consideration the size of the property, number of bedrooms, bathrooms and condition of the house. If there is a fireplace or central air conditioning, the size of the garage, a basement and all of the many other characteristics of homes will be noted as well.
The end result is a report that compares your property to others and sets forth the pricing adjustments made for the existence or non-existence of different features when compared to the other homes. The report then sets forth the appraiser's opinion of the fair market value at that time.
The report is not a guarantee that you will get that price if you list the house for sale but it is viewed by the courts when properly prepared as the opinion of an expert qualified to determine the value.