Stock Average Cost Calculator
Combine purchase history or plan an additional buy to see a weighted average cost, unused cash, and the price change required to break even.
Combine purchases or plan the next one
Advanced settings
Worked example
New average price after buying more shares
Suppose you own 100 shares bought at $50 and buy another 50 shares at $40, paying a $5 purchase fee. Your total cost is $7,005 for 150 shares, so the weighted average cost is $46.70. At a market price of $40, the position is still down $1,005. A lower average price does not erase a loss or reduce the amount of capital exposed.
Continue with the related guides
Frequently asked questions
How do I calculate the new average stock price?
Add the original purchase cost, the new purchase cost and any entered fees, then divide by total shares. Weight by share count rather than averaging the two prices.
Is average purchase cost the same as tax cost basis?
Not necessarily. This tool estimates weighted purchase cost. Sales, wash-sale adjustments, corporate actions and tax-lot elections can change tax basis; those adjustments are not included.
How does averaging down differ from dollar-cost averaging?
Averaging down means adding shares below your earlier average price. Dollar-cost averaging follows a recurring contribution schedule and can buy above or below earlier prices. Both increase invested capital.
How to use
From inputs to a result you can review
- Choose Quick Purchase Plan or Transaction History.
- Enter current holdings and a planned buy, or list each purchase with fees.
- Add a current price to see unrealized profit or loss and recovery percentage.
- Review the formula before using the result in a plan.
Known limitations
What this calculation does not know
- MVP handles purchases only; it does not process sales.
- FIFO, LIFO, specific-lot accounting, and tax rules are excluded.
- Market price is entered manually and is not a live quote.
- Fees are included only where entered.
Educational calculation only. This is not personalized investment, trading, or tax advice.
Read the guide
How to calculate average stock cost with fees
See weighted average cost, purchase fees, averaging down, break-even, and tax-basis limits.
Read the guide →Method version 1.0
Calculation logic reviewed against the published methodology and automated test cases. Last updated August 5, 2026.