Stock Average Calculator calculates the average cost of your shares and the total quantity of your shares. When you purchase the same stock multiple times, enter each transaction and get an average of it. You can use an average cost calculator to determine the average share price you paid for a security with multiple buys. This can be handy when averaging in on a stock purchase or determining your cost basis. Example: If you have 100 shares at 50 Rs rate & you bought more 10 shares at 40 Rs ra