Weighted average share price after buying more, plus unrealized profit or loss
Results update as you type. Inputs are saved on this device.
Weighted average cost per share
Weighted average = total cost of all lots ÷ total shares. Brokerage fees and lot-specific tax basis adjustments are not included.
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.
Inputs are applied directly to standard finance formulas with monthly compounding where relevant. Results are estimates in the selected currency; they do not include every tax, fee, benefit, market event or local rule. Try a conservative and an optimistic case before making a decision.
Last reviewed: August 2026. Primary references include the IRS 2026, SSA, BLS CPI, U.S. DOL, CFPB.
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.
All math runs in your browser and your inputs are never sent to a server. Settings are saved locally and share links encode the state in the URL. For information only — not investment or tax advice.