Review your portfolio to find out its net asset value per share. Calculate NAV by totaling the value of all your assets or shares and dividing by the number of shares. For example, if you have shares with a current value of $200,000 and a total of 10,000 shares, divide $200,000 by 10,000 to get the NAV per share of your current portfolio: $20.
Keep track of the fund or asset price. Calculate the new NAV whenever there is a change in price. If your portfolio value increases to $202,000, then divide $202,000 by 10,000 to get the NAV per share of your current portfolio: $20.2.
Account for every time you invest money into or withdraw money from your investments. Money invested reflects on the increase in shares. If you invest a total of $2,000 into your investment, then your share outstanding for the next day would read 10,099.01, because ($2,000/$20.2)+10,000=10,099.01. Record new investments made on a certain day at the closing of that business day. Money taken out of the portfolio also reflects on a decrease in the share outstanding. If you withdrew a total of $2,000 from your investment, then the share outstanding for the next day would read 9901, because 10,000-($2,000/$20.2)=9901.
Calculate your portfolio performance for the desired period of time by subtracting the beginning NAV from the ending NAV and dividing the result by the beginning NAV. So given that your portfolio's value now stands at $250,000 and you have a total of 10,099.01 shares, then your NAV per asset is $24.75. Therefore, to calculate your portfolio performance, subtract $20 from $24.75, giving a difference of $4.75. Then divide $4.75 by $20, giving a result of 0.2375. Your portfolio has therefore improved by 23.75 percent.