Stock Average Cost Calculator
Add each purchase to get your average cost per share, your profit or loss at the current price, and how many shares it takes to bring your average down to a target.
How average cost works
Your average cost per share is the total amount you paid divided by the number of shares you own. Buy 10 shares at $150 and 10 more at $120 and you own 20 shares for $2,700, an average of $135. The stock now has to rise only to $135, not $150, for you to break even. Averaging down lowers your break-even price but also puts more money into the same position.
For taxes, the IRS lets you report the cost of the specific shares you sell (or first-in, first-out by default) for stocks, while mutual fund shares can use average cost. Your broker reports cost basis on Form 1099-B.
Frequently asked questions
How do I calculate my average stock price?
Add up the total cost of every purchase and divide by the total number of shares. Fractional shares work the same way.
What does averaging down mean?
Buying more shares after the price falls, which lowers your average cost. It lowers your break-even point but increases how much you have riding on that one stock.
Are commissions included?
No. To include fees, add them to the purchase price of each lot (total cost ÷ shares).