Stock Average Calculator
Calculate your weighted average cost across multiple stock purchases, find how far the price needs to rise to break even, or analyse whether averaging down is worth the additional risk. Works with any currency.
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How to Use This Calculator
Tab "Average Cost"
Enter up to 5 buy lots — the number of shares and price per share for each purchase. The calculator computes the weighted average cost, total shares held, and total amount invested. Use the "+ Add lot" button to add more purchases.
Tab "Break-Even Price"
Enter your current average cost and the current market price. The result shows the percentage the stock must rise to reach your break-even point, the dollar gap per share, and whether you are currently in profit or at a loss.
Tab "Should I Average Down?"
Enter your current holding (shares and average cost) and a proposed new buy (shares and buy price). The calculator shows your new weighted average, the percentage improvement, the additional capital at risk, and your P&L at the current price.
The Formulas
Average Cost = Total Invested / Total Shares
Total Invested = Σ(Shares_i × Price_i)
Break-even percentage:
% to Break Even = (Average Cost − Current Price) / Current Price × 100
New average after averaging down:
New Average = (Old Shares × Old Avg + New Shares × New Price) / (Old Shares + New Shares)
Average improvement:
Improvement % = (Old Avg − New Avg) / Old Avg × 100
All calculations are universal and pre-tax. Brokerage fees and commissions are not included. Results are estimates.
Worked Examples
Example 1 — 3 buy lots: weighted average $42.78
An investor builds a position in a stock over three purchases as the price declines.
By buying more shares at lower prices, the investor's average cost ($41.33) is well below the initial purchase price of $50.00. The larger lots at lower prices pull the average down.
Example 2 — Break-even from $46.67 average at $40 current price
An investor has a weighted average cost of $46.67 and the stock currently trades at $40.00.
The stock needs to rise 16.68% from its current price of $40.00 to reach the break-even point of $46.67. The investor is currently sitting on a 14.29% unrealised loss.
Example 3 — Average down: 450 shares at $42.78, buy 200 more at $35
An investor holds 450 shares at an average of $42.78 and considers buying 200 more at the current price of $35.00.
Averaging down reduces the break-even from $42.78 to $40.39 — a 5.59% improvement. However, total capital at risk increases from $19,251 to $26,251. If the stock continues to fall, the loss is amplified on a larger position.
Understanding Stock Averaging
What Is Dollar Cost Averaging (DCA)?
Dollar cost averaging is the practice of investing a fixed amount at regular intervals regardless of the stock price. When the price is low you buy more shares, when it is high you buy fewer. Over time this tends to produce a lower average cost than buying all at once, because you avoid the risk of investing everything at a peak.
When Does Averaging Down Make Sense?
Averaging down works best when: (1) you believe the stock is undervalued based on fundamentals, (2) the price drop is temporary and not a sign of structural decline, (3) you have capital you can afford to lose, and (4) the position will not become an outsized percentage of your portfolio. If any of these conditions is not met, averaging down may not be appropriate.
Risks of Averaging Down
The main risk is catching a falling knife. If the stock continues to decline, you now have more capital invested at a loss. Averaging down on a stock in a genuine downtrend (broken business model, deteriorating financials, sector collapse) can turn a small loss into a catastrophic one. Always set a stop-loss or maximum position size before averaging down.
Average Cost vs Cost Basis
Your average cost (as calculated here) is the simple weighted average of your purchase prices. Your tax cost basis may differ because it includes brokerage fees, commissions, and adjustments like wash sale rules. For tax purposes, consult your broker statement or a tax professional.