Average down calculator

How averaging down works

Averaging down means buying more of a stock you already own after the price has fallen, so the blended cost of the whole position drops. This page is an average down calculator and a stock average calculator: it does that blend on numbers you type and shows the new average cost, how many shares (or dollars) the add is, and what happens to position weight if you fill in a portfolio value.

The formula is:

New average cost = (existing shares × existing average + new shares × current price) / (existing shares + new shares)

That is the same math whether you type one average or a list of prior buys. A list of buys is only a way to rebuild the current share count and average cost. Total invested is cash in at cost, not the market value of the position. Unrealized P/L now is (current price minus average cost) times current shares, on the stock you already hold.

The reverse question, how much to buy to average down to a target, rearranges the same formula. Shares to buy = current shares × (current average − target) / (target − current price). The target has to sit between the current price and the current average. If the target is at or below the price you are paying, no quantity of shares will get you there: the new average cannot fall through the purchase price.

A worked example (hypothetical)

The figures below are round numbers for illustration, not a stock, a forecast, or a recommendation.

Before the add, the stock had to rise 66.7% from $36 to get back to a $60 average. After the add you hold 183.33 shares with $9,000 in at cost, so the stock has to rise 36.4% from $36 to get back to $49.09. Unrealized loss on the original lot is still $2,400 at that instant. The new cash is spent at $36, so it is not in the hole yet.

Type a portfolio value and the weight panel is the part generic average cost calculator stocks pages usually skip. On a hypothetical $100,000 book, the position is 3.6% at $36. After adding $3,000 of new cash it is about 6.4% of $103,000. If the stock then falls another 50%, the book is hit about 1.8 points before the add and about 3.2 points after. Same arithmetic as the downside risk worksheet, with the add included.

A lower average does not change what the stock does next

Your average cost is bookkeeping. The shares you already own will make or lose the same money from today's price whether or not you add. The new money earns whatever the stock does from here, the same as if you had never owned it. A smaller percent move back to breakeven feels like progress. It is not evidence that a rebound is more likely.

Losses also take a larger gain to recover than they appear to. Pure arithmetic: a 20% drop needs a 25% rise to get back to even, a 40% drop needs about 67%, and a 50% drop needs 100%. Averaging down shrinks the percent hurdle on the blended book. It does nothing to make the climb happen. For the longer case on thesis, sunk cost, and when not to add, read should you average down on a losing stock.

Five questions before you add

Run the numbers first, then answer these in writing. If you cannot answer one clearly, that is the answer for now.

1. Why did it fall? Market, sector, one-off noise, or the thing your thesis depended on? The first three can still be a buy if the business is the one you wanted. A broken thesis is a reason to re-underwrite or exit, not to make the position larger. Re-check value with the intrinsic value calculator if the cash-flow case changed.
2. Would I buy it fresh today? Picture a friend handing you cash with no lot and no history. If you would not start the position at this price, adding is mostly about feeling better, not about a new investment.
3. What will the position weigh after the add, versus my cap? Set a maximum single-stock weight before you need it. Type your portfolio value above and read weight after the add. If it would push you past the cap, the answer is no, or a smaller add. The concentrated portfolio calculator shows how a large name moves the whole book. For how much of a portfolio to put in individual stocks at all, see what percentage of a portfolio should be individual stocks.
4. Is this the best use of this cash? The alternative is not “do nothing.” It is every other place the money could go: the next idea, a broad fund, or cash you actually need. If the stock would not make the list as a new position, averaging down is a story about the old one.
5. What do I do if it falls another 30%? Write it down now: a price and a metric that would make you sell, and a rule that you will not add again on the same thesis. The weight panel's 30% and 50% hits are there so that sentence has a number. One planned add is a plan. Adding every time the quote prints lower is how a small line becomes the whole risk.

Dollar-cost averaging is not averaging down

Dollar-cost averaging (DCA) means investing a fixed amount on a schedule, whatever the price does. Averaging down is a choice to buy because a holding already fell. Rebalancing back to a target weight is a third thing. People mix the three up, and the mix is how a one-off add turns into an unplanned concentration.

This calculator measures one add. It does not run a calendar of future buys, and it does not assume the stock mean-reverts. If you are contributing on a schedule to a diversified fund, you are closer to DCA than to averaging down on a single name. A single company can go to zero. That difference is the whole point of the five questions.

Wash sales

In a U.S. taxable account there is a timing wrinkle if you are also thinking about selling at a loss. Under wash sale rules, buying a substantially identical security within 30 days before or after a loss sale can disallow deducting that loss. Adding shortly before or after a tax-loss sale can undo it. Read the Investor.gov glossary on wash sales. This tool does not compute tax lots. Check with a tax professional for your situation.

None of this is a recommendation to buy or sell any security. The starting figures on the calculator are hypothetical. If you want the written research behind Outpick names, that lives on the membership side of the site, not in this arithmetic.