Average Down & DCA Calculator — Blended Cost Basis
Calculate your weighted average cost basis and break-even price across multiple buys at different prices and quantities. No commission tracking.
25.0000 units · total cost $2,200.00
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Averaging down means your cost basis is weighted, not averaged
You buy 10 shares at $100, then 15 more at $80. Your average price is not $90 — it is ($100 × 10 + $80 × 15) / (10 + 15) = $1,600 / 25 = $88. The lower price pulls your average down, but only by weight of quantity. If you had bought only 2 shares at $80, your average would be $98.40, not $90.
Every new entry changes your break-even point
Before averaging down, if you held 10 shares at $100, you break even at $100. After buying 15 shares at $80, your break-even drops to $88. This tool recalculates your weighted average and break-even after each entry you add. It also shows your profit or loss at any target price: if the price reaches $95, your total P&L is ($95 − $88) × 25 = $175, or 7.95% gain.
Commissions and slippage are not included
This calculator works with the prices and quantities you enter, with no deductions for trading fees, commissions, spreads, or bid-ask slippage. If you pay $10 per trade, add that to your effective cost basis manually to match reality.
You can add as many entries as needed
Click "+ Add another buy" to model any number of positions at different prices and quantities. The calculator validates each entry (negative prices and zero quantities are skipped) and updates your weighted average and target P&L in real time.
Learn more: Position Size Calculator to plan each new entry, or Kelly Criterion Calculator for optimal position sizing.
How to use the Average Down / DCA Calculator
Takes about a minute. No signup, no download, your data stays in your browser.
- 1Open the tool. Scroll up to the Average Down / DCA Calculator above — it loads instantly in your browser, no install needed.
- 2Enter your values. The fields come pre-filled with realistic defaults so you can see how it works — replace them with your own numbers.
- 3Read the result. The output updates instantly. Copy or share it — nothing is uploaded to a server, everything stays on your device.
Frequently asked questions
Common questions about the Average Down / DCA Calculator.
Does this tool include trading fees or commissions?
No. The calculator uses only the price and quantity you enter. If you pay trading fees, bid-ask spreads, or commissions, add them manually to your effective cost basis to match your real total cost.
What happens if I enter a negative price or zero quantity?
Entries with negative prices or zero or negative quantities are automatically skipped and do not affect your weighted average. You must have at least one valid entry (positive price and positive quantity) to calculate a result.
How is the weighted average cost calculated?
The tool sums the product of price × quantity for all entries, then divides by total quantity: (price₁ × qty₁ + price₂ × qty₂ + ...) / (qty₁ + qty₂ + ...). Example: 10 @ $100 + 15 @ $80 = ($1,000 + $1,200) / 25 = $88.
How does the target P&L calculation work?
P&L in dollars = (target price − average price) × total quantity. P&L in percent = (target price − average price) / average price × 100%. If your average is $88, total quantity is 25, and the price reaches $95, your gain is ($95 − $88) × 25 = $175, or 7.95%.
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