Stock Average Price Calculator

How to use the stock average calculator

1. In the “Average price” mode, enter the shares and the price of each purchase. Add a row for each buy, up to ten.
2. Enter the current price if you want to see the market value and the profit or loss.
3. In the “Reach a target average” mode, enter the shares you own, your average price, the new buy price and the average you want.
4. Read the shares to buy and the cost of the new purchase. If the target is not between your average and the new price, it cannot be reached.

The average price formula

Your average price is the total you paid divided by the total number of shares. A new purchase at a lower price pulls the average down in proportion to its size, which is why each step of averaging down needs more shares than the last to move the average by the same amount.

To reach a target average after buying at a new price, the shares to buy are the shares you own times the gap between your average and the target, divided by the gap between the target and the new price.

Worked example

You bought 100 shares at $50, and the stock now trades at $40.

• Buy 100 more at $40: $5,000 + $4,000 = $9,000 for 200 shares, an average of $45.00.
• To bring the average to $42 instead: 100 × ($50 − $42) ÷ ($42 − $40) = 400 shares, or $16,000 more.
• You would then hold 500 shares worth $20,000 at $40, with $21,000 invested: a much bigger position in a stock that has been falling.

Averaging down lowers the price you need to break even, but it also adds to a losing position. Set your stop and your maximum position size before you add.