Definition of 'Graham Number'
A figure that measures a stock's fundamental value by taking into account the company's earnings per share and book value per share. The Graham number is the upper bound of the price range that a defensive investor should pay for the stock. According to the theory, any stock price below the Graham number is considered undervalued, and thus worth investing in. The formula is as follows:
Investopedia explains 'Graham Number'
The Graham number is named after the "father of value investing," Benjamin Graham. It is used as a general test when trying to identify stocks that are currently selling for a good price. The 22.5 is included in the number to account for Graham's belief that the price to earnings ratio should not be over 15 and the price to book ratio should not be over 1.5 (15 x 1.5 = 22.5). It does leaves out many fundamental characteristics which make up a good investment, and is not effective for the majority of medium- to large-cap stocks.
For example, if the earning per share is $1.50, book value per share is $10, the Graham number would be 18.37. If the stock price is $16, you should buy the stock. If the stock price is $19, and you own it, you should sell the stock.