Offer your thoughts or opinion on the input financial query or topic using your financial background.

Compute average price even if I do not have the prices before
What I do have is this (sample only): Stock X: Average Price of all I purchased before = 80 Total Shares = 200 So if Stock X's price today is 100 how do I know how much my average price will be? Using your sample if you buy 100 new shares and the price is 85 for the purpose of this example your previous total cost is $16,000 ($80 average cost * 200 shares).  With the new example you are adding $8500 to your total cost (100 new shares * $85 example cost per share)  that gives us a total cost of $24,500 and 300 shares. $24,500/300 gives us an average cost of $81.67 per share. As long as you have the average cost and the number of shares you can calculate a new average without knowing what the price was for each transaction. It may still become important to find the price information for tax purposes if you do not sell all of those shares at once and use FIFO for your taxes.