The first thing you need to know about deciding a property's worth is that it is not an exact science. Various factors affect the selling price. These include local and national market conditions, the sellers situation and relative timescales, the desirability of the location, property condition and the number of similar style properties for sale, or recently sold, in the area. The list is endless, which is why it is important in determining value to take a broad approach in what your home is likely to achieve. It is crucial to physically visit and view a property before nailing down the value. This simply can't be done 'online' or before the appraisal. It's important the valuation is well thought out and all factors are considered. The valuation should be calculated and realistic. If you do decide to sell, a mortgage valuer will need to see evidence that your buyers are paying the right price by looking at comparable sold prices across agents locally, and the valuation should be impartial.