How does Average Purchase Price work?

Within PDT, we display the average purchase price (APP) of a security when you open the detail page of that security in your portfolio. But what does this number tell you, and how is it calculated?

The average purchase price shows how much you have paid on average per share across all your purchases of that security.

The calculation:

APP = total purchase amount ÷ total number of shares

Example

Suppose you buy 10 shares of Alstom at €25 each (10 × €25 = €250), and later you buy another 10 shares at €20 each (10 × €20 = €200).

Your total cost will then be €250 + €200 = €450. With 20 shares held, your average purchase price will be €22.50.

APP = €450 ÷ 20 = €22.50

Exceptions

• Sold positions: If you fully sell a security and later buy it again, the historical APP is not included in the new calculation. When you reopen the position, a new APP is calculated from scratch.
• ISIN changes: When a security receives a new ISIN (for example, due to a takeover), we do carry over the original APP to the new security. This prevents your APP from being “reset” after a corporate action. At DEGIRO, for instance, an ISIN change is processed as a full sale and the opening of a new position, which causes the average purchase price to be recalculated.