Understand the numbers
When shares are purchased at different prices, a simple average of the purchase prices can be misleading. This calculator uses a weighted average so larger share purchases have the correct influence on your total cost basis.
Calculation method
Each purchase price is multiplied by the number of shares in that lot. Those purchase costs are added together and divided by the total number of shares to estimate the weighted average price per share.
Example
Example: buying 10 shares at $50 costs $500 and buying 20 more at $40 costs $800. The combined $1,300 cost divided by 30 shares produces an average price of about $43.33 per share before fees or taxes.
Useful checks
- Enter every purchase lot you want included in the position.
- Use current price to estimate unrealized gain or loss.
- Broker-reported tax basis may differ when commissions, corporate actions or tax adjustments apply.