βοΈ Stock Average Down Calculator
Your new cost basis after buying the dip.
New average cost per share
Estimates for planning only, not financial advice.
Own 100 shares at $50 and buy 100 more at $40, and your average cost drops to $45 a share. The stock only needs to recover to $45, not $50, for you to break even. That is the appeal of averaging down, and also the trap: the math always looks good, even when the company does not.
How to Use This Calculator
Enter your current share count and average price, then the new purchase. The calculator returns the new weighted average, total cost basis, and the breakeven price, the number the stock must reach for you to be whole.
Enter current shares and your existing average cost per share from your brokerage statement.
Enter the new buy: shares and price. The calculator weights by dollars, not by share count.
Read the new average and breakeven, then ask the hard question below before you buy.
The Formula
It is a weighted average by dollars invested. Note the weighting subtlety: buying 100 shares at $40 against 100 at $50 moves the average to $45, exactly midway, because the dollar amounts are close. But buying 10 shares at $40 against 100 at $50 barely moves it to $49.09. Small add-on buys are psychological comfort, not math.
Worked Example
100 shares at $50 ($5,000) plus 100 shares at $40 ($4,000). Total: 200 shares, $9,000 cost. New average: 9,000 / 200 = $45. Breakeven: $45. The stock fell 20 percent from your first buy, but you now need only an 11.1 percent recovery from $40.50 (roughly) to break even. That shrinking hurdle is why averaging down feels smart, and it is, provided the business is fine and only the price was wrong.
When Averaging Down Works
Averaging down is rational when the thesis is intact and the price drop is sentiment, sector rotation, or a market-wide selloff. The checklist: revenue and cash flow still growing, the reason you bought still true, the position size stays within your risk limits after adding, and you would buy this stock fresh today at this price. If all four hold, lowering your basis is disciplined value investing, not denial.
When It Is Catching a Falling Knife
The failure mode has a name for a reason. Averaging down into a broken thesis, fraud, permanent demand loss, a balance sheet in distress, converts a small loss into a large one and concentrates your portfolio in your worst idea. Warning signs: you are averaging down to "get back to even" rather than because the stock is cheap, the position is now oversized, or you cannot articulate what changed except the price. Professional money managers usually size positions once and let losers go; amateurs double down. Be honest about which game you are playing.
Averaging Down vs Dollar-Cost Averaging
These get confused constantly. Dollar-cost averaging is buying on a schedule regardless of price, a disciplined entry strategy. Averaging down is buying specifically because the price fell, a reactive decision. DCA into an index fund is close to optimal for most people; averaging down into a single stock is a concentrated bet that demands a real thesis. If you want the scheduled version, our savings calculator models regular investing, and the stock return calculator scores the trade once you exit.
Averaging Down vs Catching a Falling Knife
Averaging down works when the thesis is intact and the price is wrong; it destroys capital when the thesis is broken and the price is right. The difference is the reason for the fall. A great business down 20 percent on a market-wide selloff is a candidate. A company down 60 percent on fraud allegations, a lost contract, or a broken balance sheet is a value trap, and averaging into it concentrates you in your worst idea.
Three rules keep averaging honest. First, pre-commit: decide the buy levels and sizes before the fall, not during it. Second, cap the position: no single stock above 5 to 10 percent of the portfolio no matter how cheap it looks. Third, re-underwrite every add: write one paragraph on why the business is worth more than the price before each purchase. If you cannot write it, you are not averaging down; you are refusing to admit a mistake. Index fund investors can ignore all of this: regular contributions are automatic averaging with diversification built in.
Average Down With Rules, Not Hope
Averaging down works when the thesis is intact and the price is wrong; it destroys capital when the thesis is broken and the price is right. Write your averaging rules before you need them: maximum position size, the fundamental triggers that would stop you, and a clear distinction between a sale and a buying opportunity. Then let the calculator track the blended cost while you track the business. Discipline turns averaging into strategy; hope turns it into a habit of catching knives.
Estimates for planning only, not financial advice.
Frequently Asked Questions
How do you calculate average share price?
Weight by dollars: (shares1 x price1 + shares2 x price2) divided by total shares. 100 shares at $50 plus 100 at $40 gives (5000 + 4000) / 200 = $45. Your brokerage shows this as cost basis per share. Note this is the average purchase price, not including commissions; add total commissions divided by total shares for the true economic breakeven.
What is averaging down in stocks?
Buying more shares of a stock you own after the price falls, which lowers your average cost per share. 100 shares at $50 averaged with 100 at $40 gives a $45 average, so the stock needs to reach $45, not $50, for you to break even.
Is averaging down a good strategy?
It depends on why the stock fell. If the business is healthy and only the price dropped, it lowers your breakeven rationally. If the thesis is broken, it concentrates losses in a bad idea. Never average down just to get back to even faster.
How low does the stock need to go back to for me to break even?
To your new weighted average price. After averaging 100 shares at $50 with 100 at $40, breakeven is $45. Commissions and taxes nudge the true breakeven slightly higher, so treat the calculator's figure as the minimum. If you sell below the average but above your original $50 purchase, you still book a loss on the averaged position even though the second lot profited.
Does buying a small amount help my average?
Barely. Averaging is dollar-weighted: 10 shares at $40 against 100 at $50 moves the average from $50 to only $49.09. To move the needle, the new purchase must be meaningful relative to the existing position. As a rule of thumb, the new money should be at least a third of the position's current value to shift the average more than a few percent.
What is the difference between averaging down and dollar-cost averaging?
Dollar-cost averaging buys on a fixed schedule regardless of price. Averaging down buys reactively because the price fell. DCA is a disciplined entry plan; averaging down is a judgment call about a specific stock being cheap. DCA works without any forecasting skill, while averaging down demands you be right about value, which is why DCA suits index funds and averaging down demands real research.
Can averaging down increase my risk?
Yes, it concentrates your portfolio. Doubling down on a falling stock makes it a bigger slice of your holdings at exactly the moment it is performing worst. Set a maximum position size (say 5 to 10 percent of your portfolio) and stop adding past it.
Should I average down on an index fund?
That is just regular investing, and it is fine. Index funds do not go to zero the way single stocks can, so adding on dips is standard dollar-cost averaging. The falling-knife risk applies to individual companies, not broad indexes. One caveat: keep your overall asset allocation in check, since enthusiastic dip-buying can leave you overexposed to equities after a long rally.
How do I know if a falling stock is a value or a trap?
Check the thesis: is revenue growing, is the balance sheet sound, is the dividend covered, and would you buy it fresh today? If yes, the dip may be opportunity. If the answers are no, or you are buying mainly to lower your average, it is probably a trap.
Do wash sale rules affect averaging down?
Only if you sell at a loss and rebuy within 30 days. Averaging down by itself, just buying more, triggers no wash sale. But if you harvest the loss by selling and then buy back within 30 days before or after, the loss is disallowed.