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Free alpha and beta calculator. Measure your portfolio's market sensitivity (beta) and excess risk-adjusted return (alpha) against a benchmark index.
Stock Average Calculator
Calculate your weighted average cost basis across multiple stock purchases. See per-lot P/L, position value, break-even price, and average-down scenario analysis.
For average-down analysis
Average Cost Basisโง
$153.33
60 shares total
Total Investedโง
$9,200.00
6 purchases
Position Valueโง
$10,500.00
At $175.00/share
Unrealized P/Lโง
$1,300.00
14.1% gain
Break-Even Priceโง
$153.33
Sell above this to profit
New Avg (after buy)โง
$156.25
+$2.92 change
P/L by Purchase Lot
Lot 1$150.00
+16.7%
Lot 2$160.00
+9.4%
Lot 3$140.00
+25.0%
Lot 4$155.00
+12.9%
Lot 5$145.00
+20.7%
Lot 6$170.00
+2.9%
Purchase Lot Details
| Lot | Price | Shares | Cost | Value | P/L |
|---|---|---|---|---|---|
| 1 | $150.00 | 10 | $1,500.00 | $1,750.00 | $250.00 (16.7%) |
| 2 | $160.00 | 10 | $1,600.00 | $1,750.00 | $150.00 (9.4%) |
| 3 | $140.00 | 10 | $1,400.00 | $1,750.00 | $350.00 (25.0%) |
| 4 | $155.00 | 10 | $1,550.00 | $1,750.00 | $200.00 (12.9%) |
| 5 | $145.00 | 10 | $1,450.00 | $1,750.00 | $300.00 (20.7%) |
| 6 | $170.00 | 10 | $1,700.00 | $1,750.00 | $50.00 (2.9%) |
| Total | $153.33 | 60 | $9,200.00 | $10,500.00 | $1,300.00 (14.1%) |
Average-Down Scenarios (at $165.00)
| Add Shares | Add Cost | New Avg | Reduction |
|---|---|---|---|
| +10 | $1,650.00 | $155.00 | โ-$1.67 |
| +25 | $4,125.00 | $156.76 | โ-$3.43 |
| +50 | $8,250.00 | $158.64 | โ-$5.30 |
| +100 | $16,500.00 | $160.63 | โ-$7.29 |
| +200 | $33,000.00 | $162.31 | โ-$8.97 |
Planning notes, formulas, and examples
About the Stock Average Calculator
When you buy a stock multiple times at different prices, knowing your weighted average cost basis is essential for making informed sell decisions and calculating taxes. This calculator takes all your purchase lots and computes the overall average cost, position profit/loss, and break-even price.
The per-lot analysis breaks down P/L for each individual purchase, revealing which entries are profitable and which are underwater. Color-coded bars give you instant visual feedback on your best and worst-timed buys. This is the same data your brokerage tracks, but presented in a cleaner analytical format.
The average-down simulator shows exactly how buying additional shares would lower (or raise) your average cost. Enter a potential buy price and shares, and the calculator maps out multiple scenarios showing how many shares you'd need to bring your average to specific levels. This is useful when deciding whether a new lot meaningfully improves your break-even price.
When This Page Helps
Use this to track your true cost basis after multiple purchases, DRIP reinvestments, or partial sales. It makes the break-even price and unrealized profit or loss easy to see before you place the next order.
How to Use the Inputs
- Enter each purchase as Price:Shares, one per line.
- Set the current market price for P/L calculations.
- Review your average cost basis and total position value.
- Check per-lot P/L to see which entries are profitable.
- Enter a next-buy price and shares for average-down analysis.
- Use the scenario table to plan optimal position sizing.
Formula used
Average Cost = Total Cost / Total Shares
Total Cost = ฮฃ(Price_i ร Shares_i)
Unrealized P/L = (Current Price โ Avg Cost) ร Total Shares
Break-Even Price = Average Cost
New Average = (Old Cost + New Purchase) / (Old Shares + New Shares)Example Calculation
Result: Average Cost: $153.33, 60 shares, +14.1% unrealized gain
Six DCA purchases at different prices average to $153.33/share. At $175, the 60-share position is worth $10,500 with $1,300 (14.1%) unrealized gain.
Tips & Best Practices
- DCA (Dollar Cost Averaging) naturally averages your cost when a stock fluctuates โ but only helps if the stock eventually recovers.
- Set a maximum position size before averaging down. Don't let a losing trade become oversized.
- Reinvested dividends lower your effective cost basis โ track DRIP shares separately.
- Use specific lot identification when selling to minimize taxes (sell highest-cost lots first for smallest gain).
- Your break-even is your average cost โ set alerts at this price to know when you're back to flat.
Understanding Average Cost
Your weighted average cost basis is the total dollars spent divided by total shares owned. That number is what matters when you want a clean break-even level or want to estimate the gain on the full position.
Average-Down Decisions
Adding shares at a lower price can improve your average cost, but it only helps if the underlying position still makes sense. The scenario table is most useful when you want to compare the effect of a small add versus a larger commitment.
Sources & Methodology
Last updated:
Methodology
This worksheet totals the entered purchase lots, divides total dollars invested by total shares to estimate weighted-average cost basis, and uses the entered current price to compute unrealized gain or loss on both the whole position and each lot. The average-down simulator simply adds a hypothetical new purchase to the existing cost and share totals, then recomputes the blended average price.
The result is a position-tracking worksheet, not a broker record of tax lots. It does not replace broker-specific lot-identification rules, wash-sale adjustments, commissions, or account-level tax reporting unless the user includes those items in the entered lot data.
Sources
- Basis and Cost Basis (Investor.gov / U.S. Securities and Exchange Commission) โ SEC investor glossary reference for the core cost-basis concept used in lot tracking and gain calculations.
- Publication 550 (2025), Investment Income and Expenses (Internal Revenue Service) โ IRS reference for basis, lot identification, DRIP treatment, and stock-split context in taxable accounts.
Frequently Asked Questions
The weighted average price of all your shares. Total dollars invested divided by total shares owned. Used for tax calculations and P/L tracking.
Only if you still believe in the investment thesis. Averaging down on a declining stock with broken fundamentals just increases losses. Average down on temporary dips, not broken companies.
Your total cost stays the same, but shares double (for 2:1 split). So average cost per share halves. Total position value is unchanged.
When you sell, your capital gain is (Sell Price โ Average Cost) ร Shares. Lower average cost = higher taxable gain. You can also use specific lot identification for tax optimization.
FIFO sells your oldest shares first. Average cost uses the weighted average. For stocks (not mutual funds), specific lot identification is usually optimal for tax purposes.
Both. Overall average gives your break-even. Per-lot tracking enables tax-loss harvesting โ selling underwater lots to offset gains elsewhere.
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