There are 
                  several methods used to value companies and their stocks. They 
                  attempt to give an estimate of their fair value, by using fundamental 
                  economic criteria. This theoretical valuation has to be perfected 
                  with market criteria, as the final purpose is to determine potential 
                  market prices.
                Fundamental 
                  criteria (fair value)
                The most 
                  theoretically sound stock valuation method is called 
                  income valuation or the discounted cash flow (DCF) method, 
                  involving discounting the profits (dividends, earnings, 
                  or cash flows) the stock will bring to the stockholder in the 
                  foreseeable future, and a final value on disposition. The discount 
                  rate normally has to include a risk premium which is commonly 
                  based on the capital asset pricing model.
                Approximate 
                  valuation approaches
                Average 
                  growth approximation: Assuming that two stocks have the 
                  same earnings growth, the one with a lower P/E is a better value. 
                  The P/E method is perhaps the most commonly used valuation method 
                  in the stock brokerage industry. By using comparison firms, 
                  a target price/earnings (or P/E) ratio is selected for the company, 
                  and then the future earnings of the company are estimated. The 
                  valuation's fair price is simply estimated earnings times target 
                  P/E. This model is essentially the same model as Gordon's model, 
                  if k-g is estimated as the dividend payout ratio (D/E) divided 
                  by the target P/E ratio.
                
                  Constant growth approximation: The Gordon model or Gordon's 
                  growth model[1] 
                  is the best known of a class of discounted dividend models. 
                  It assumes that dividends will increase at a constant growth 
                  rate (less than the discount rate) forever. The valuation is 
                  given by the formula:
                 
                   . .
and the 
                  following table defines each symbol:
                
                   
                   
                    | Symbol | Meaning | Units | 
                   
                    |  | estimated stock price | $ or € or £ | 
                   
                    |  | last dividend paid | $ or € or £ | 
                   
                    |  | discount rate | % | 
                   
                    |  | the growth rate of the dividends | % | 
                   
                
                [1]
                Limited 
                  high-growth period approximation: When a stock has a significantly 
                  higher growth rate than its peers, it is sometimes assumed that 
                  the earnings growth rate will be sustained for a short time 
                  (say, 5 years), and then the growth rate will revert to the 
                  mean. This is probably the most rigorous approximation that 
                  is practical [2].
                Market 
                  criteria (potential price)
                Some feel 
                  that if the stock is listed in a well organized stock market, 
                  with a large volume of transactions, the listed price will be 
                  close to the estimated fair value. This is called the efficient market hypothesis.
                On the other 
                  hand, studies made in the field of behavioral finance tend to 
                  show that deviations from the fair price are rather common, 
                  and sometimes quite large.
                Thus, in 
                  addition to fundamental economic criteria, market criteria also 
                  have to be taken into account market-based valuation. Valuing 
                  a stock is not only to estimate its fair value, but also to 
                  determine its potential price range, taking into account 
                  market behavior aspects. One of the behavioral valuation tools 
                  is the stock image, a coefficient that bridges the theoretical 
                  fair value and the market price.
                On-line 
                  valuation calculators
                
                  
                References
                
                External 
                  links