About the Stock Average Price Calculator
Buying the same stock over time — through regular investing or by adding to a position — leaves you with shares at different prices. Your average cost is the total you paid divided by the total shares, which is also your break-even price before fees.
Add as many purchases as you need with the "Add Purchase" button. Fractional shares are supported.
How It Works
For each purchase, the calculator multiplies shares by price. It adds these amounts to get the total invested and divides by the total number of shares.
If you enter a current price, it multiplies your total shares by that price and compares the result with the total invested to show unrealized profit or loss and return.
Formula
Example
You bought 10 shares at $100, 20 shares at $85, and 5.5 shares at $120. The stock now trades at $110.
Inputs
- Purchases
- 3
- Current price
- $110.00
Results
- Total shares
- 35.5
- Total invested
- $3,360.00
- Average cost
- $94.65
- Unrealized P/L
- +$545.00
Assumptions & Limitations
- Commissions and fees are not included; add them to the purchase price if you want them in your cost basis.
- No sales: this averages purchases only. Tax cost-basis methods (FIFO, specific lot) matter when you sell part of a position.
- Stock splits should be reflected by adjusting shares and prices before entering them.
Understanding Your Results
- Average Cost per Share: What each share cost you on average — your break-even price before fees.
- Unrealized Profit / Loss: Gain or loss on paper at the current price; it is realized only when you sell.