Stock Average Calculator
Your average cost per share, break-even price, and gain across every purchase
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Quick summary
Add each purchase (shares, price, and any commission) to get your blended average cost per share and total cost basis — the number that determines your break-even and taxable gain. Enter a current price to see unrealized profit or loss. Buying more at a lower price ('averaging down') pulls your average — and break-even — down; buying higher pulls it up. Pure math, no market data needed.
Reviewed by Simple Calculators TeamLast reviewed
For planning only — not financial or tax advice. Results are estimates based on your inputs and the stated assumptions. Confirm important decisions with a qualified professional.
How to use this calculator
- Enter the inputs requested by the calculator.
- Choose the units or options that match your situation and review the assumptions.
- Run or update the calculation to see the result.
- Review the result, breakdown, and formulas shown on the page.
- Check the inputs, units, dates, and limitations before saving or sharing the result.
Frequently asked questions
How do I calculate my average stock price?
Total amount spent divided by total shares owned. Buy 10 shares at $100 ($1,000) and 10 more at $80 ($800): that's $1,800 for 20 shares, an average of $90/share. Include commissions in the total for the true cost basis.
What does 'averaging down' mean?
Buying more of a stock you already own at a lower price, which lowers your average cost per share. If your average was $100 and you buy more at $80, your new average falls between the two — meaning the stock needs to recover less for you to break even. It also increases your position (and risk) in a falling stock.
What is cost basis and why does it matter?
Cost basis is the total you paid, including fees — the figure the IRS uses to compute your capital gain when you sell (sale proceeds minus cost basis). Tracking it accurately across multiple purchases is essential for correct tax reporting; brokers report it, but verifying it yourself avoids surprises.
What is my break-even price?
Your average cost per share — the price the stock must reach for your whole position to be worth what you paid. Below it you're down; above it you're up (before taxes and any selling commission). Averaging down lowers this threshold.
Key terms
- Cost Basis
- Total invested including commissions — the basis for both break-even and capital-gains tax.
- Average Down
- Buying more at a lower price to reduce your average cost per share.
- Break-Even Price
- The average cost per share — where the position returns to zero gain.
- Unrealized Gain
- Paper profit at the current price, before you sell; not yet taxable.
Methodology, sources & limitations
This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.
For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.