Stock Average Down Planner
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Purchase Lots
How to Calculate Average Cost When Buying More Shares
When you buy additional shares of a stock at a different price, your average cost per share changes. This is called averaging down (buying more at lower prices) or averaging up (buying more at higher prices). Knowing your true average cost is essential for calculating break-even and profit targets.
The weighted average formula accounts for both the price and quantity of each purchase. If you bought 50 shares at $100 and 75 shares at $85, your average isn't simply ($100 + $85) / 2 = $92.50. It's (50 × $100 + 75 × $85) / 125 = **$91.00**. The second purchase has more weight because you bought more shares.
Averaging down is a legitimate strategy when you have conviction in a stock that has declined due to market conditions rather than fundamental deterioration. It lowers your break-even price, meaning the stock doesn't have to recover to its original price for you to profit.
The danger: averaging down on a stock that's declining for good reason. This is called "catching a falling knife." If a company's earnings are deteriorating, adding to a losing position just increases your exposure to a bad investment. Never average down more than your position sizing rules allow — if a position was supposed to be 5% of your portfolio, don't let it become 15% just because you kept buying the dip.
Formula
Average Cost = (Shares₁ × Price₁ + Shares₂ × Price₂ + ...) ÷ Total Shares
Example
You bought AAPL in three lots: - 30 shares at $190 - 50 shares at $175 - 20 shares at $165
Total cost: (30 × $190) + (50 × $175) + (20 × $165) = $5,700 + $8,750 + $3,300 = $17,750. Total shares: 100. Average cost: $17,750 ÷ 100 = $177.50 per share.
If AAPL recovers to $185, your profit is ($185 − $177.50) × 100 = $750 (4.2% gain).
Frequently Asked Questions
Is averaging down a good strategy?
It can be — if the stock is fundamentally sound and the decline is temporary. Averaging down on a quality company during a market pullback lowers your break-even and increases your position for the recovery. Averaging down on a stock with deteriorating fundamentals is a recipe for larger losses.
How do you calculate average stock price with multiple purchases?
Multiply each purchase price by the number of shares bought at that price. Add all those amounts together to get total cost. Divide by total shares owned. This gives you the weighted average cost per share.
When should I stop averaging down?
Set a maximum position size before you start. If you planned for 5% of your portfolio in this stock, don't exceed it regardless of how cheap the stock gets. Also reassess the thesis: if the reason you bought has changed (earnings miss, industry shift), stop adding and consider cutting losses.
What is the difference between dollar cost averaging and averaging down?
Dollar cost averaging (DCA) is buying a fixed dollar amount on a regular schedule regardless of price — it's a passive, long-term strategy. Averaging down is actively buying more shares specifically because the price has dropped — it's a deliberate decision to increase a position at a lower price. DCA is systematic; averaging down is discretionary.
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