The new weighted average is the price at which the combined lots have zero gain before fees and taxes. Total cost and total shares show the denominator behind that figure; unrealized return compares current market value with the modeled cost basis.
Corporate actions, fractional-share rounding, commissions, wash-sale rules and broker-specific tax-basis elections can change the reported basis. Averaging down also increases the amount exposed to one security.
Weighted average share price after buying more, plus unrealized profit or loss
A stock average price is a weighted cost, not the simple average of two prices. Enter the shares and average price you already own, then the size and price of an additional purchase. The calculator combines both lots, shows the new break-even cost per share, and estimates the unrealized gain or loss at the current market price.
The new weighted average is the price at which the combined lots have zero gain before fees and taxes. Total cost and total shares show the denominator behind that figure; unrealized return compares current market value with the modeled cost basis.
Corporate actions, fractional-share rounding, commissions, wash-sale rules and broker-specific tax-basis elections can change the reported basis. Averaging down also increases the amount exposed to one security.
UNDERSTAND THE NUMBERS
Fixed educational example · independent of your inputs above. $ means US dollars; these are not current rate quotes or return forecasts.
Suppose you own 100 shares bought at $100. Compare keeping them with buying another 100 at $60. In both cases, examine a later market price of $50. Fees and taxes are excluded.
| Position | Average cost | Loss at $50 |
|---|---|---|
| Keep 100 shares | $100 | $-5,000 |
| Buy 100 more | $80 | $-6,000 |
The average falls from $100 to $80, but invested cash rises from $10,000 to $16,000. At $50, the percentage loss improves while the dollar loss grows. Average cost answers where your position breaks even before costs; it does not establish what the business is worth.
This weighted average is not a tax-lot ledger. A broker may calculate taxable gains using specific lots, and currency conversion or corporate actions can change your records. Keep the purchase dates and fees separately.
Keep the added purchase fixed and move the market price to $40, $60 and $80. Compare the loss amount with the amount you can afford to lose, not just the percentage needed to break even.
Include exit fees and estimated tax →Prepared by EconoPi · examples and explanations reviewed September 19, 2026. Tables are our calculations under stated assumptions, not forecasts or recommendations by the referenced organizations.
Add the cost of every purchase and divide by the total number of shares. One hundred shares at $50 plus fifty at $40 cost $7,000 across 150 shares, for a $46.67 average.
No. It lowers the average only when the additional purchase price is below the current average. Buying above the current average raises it.
No. Add fees to each lot's cost basis separately if your broker charges them or if local tax rules require basis adjustments.
A lower average does not improve the business or remove risk. Reassess the investment thesis and position size before committing more capital.
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