Stock Average Price Calculator
Last updated: November 5, 2026
Calculate the weighted average share price after an additional stock purchase.
New average share price
—
- Total shares: —
- Total cost basis: —
- Change from prior average: —
On this page
Quick summary: Calculate the weighted average share price after an additional stock purchase.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Calculate the weighted average share price after an additional stock purchase.
How to use it
Enter Existing shares; Existing average price per share ($); New shares purchased; New purchase price per share ($); Trading fees ($). Select Calculate to update the results.
How the calculation works
The new average price is total existing and new cost, including fees, divided by total shares.
Worked example: starting scenario
| Existing shares | 150 |
|---|---|
| Existing average price per share ($) | 82 |
| New shares purchased | 75 |
| New purchase price per share ($) | 64 |
| Trading fees ($) | 5 |
| New average share price | $76.02 |
|---|---|
| Total shares | 225 |
| Total cost basis | $17,105.00 |
| Change from prior average | -$5.98 |
Important limitations
Tax-lot identification, wash-sale adjustments, return of capital and corporate actions can affect tax basis.
Average price is weighted by shares
Buying 100 shares at $10 and 50 shares at $20 costs $2,000 before fees. The average is $2,000 divided by 150 shares, or about $13.33; averaging the two quoted prices would incorrectly give $15. Fractional shares are valid here. The displayed cost average is not a determination of which tax lot is sold.