Let's say you buy three shares at prices of $5, $5 and $10. You paid a total of $20 for the three shares. Now you sell 2 of them for $20 each ($40 in total), a

Let's say you buy three shares at prices of $5, $5 and $10. You paid a total of $20 for the three shares. Now you sell 2 of them for $20 each ($40 in total), and have 1 share remaining. You want to calculate realized P&L using the average cost method. The average cost per share is $20/3, so the P&L is $40-(20/3).