Stock average calculator

The only discount where you already own the product.

Your buys

2 lots

Positions stay in your browser. Closes are official end-of-day data; type any price you like.

Average cost per share$40.00
Needs +14.3% to break even
Total shares
200
Total cost
$8,000.00
Worth now
$7,000.00
Profit / loss
−$1,000 (-12.5%)

Before your last buy the average was $50.00 and the stock needed +42.9% to get you back to even. Now it needs +14.3%. The loss itself didn't shrink; you just own more of it ($5,000.00 at risk became $8,000.00).

$30.00┆ avg $40.00┃ now $35.00$50.00
Each circle is a buy (bigger = more shares). Dashed: your average. Solid: the price now.

How many shares to reach a target average?

The target has to sit between the price you can buy at and your current average ($40.00). No amount of buying gets there otherwise.

What averaging down actually does

It lowers your breakeven, not your loss. Buy 100 shares at $50, watch them slide to $30, buy 100 more: your average is $40, and the stock now needs a 33% rise to get you back to even instead of 67%. That feels like progress. It is also twice as much money in the thing that just fell 40%.

So the calculator shows both sides at once: the rise you need before and after your last buy, and the dollars at risk before and after. The arithmetic only works in your favour if the company is still the company you bought. The price chart can't tell you that; the filings sometimes can.

The target finder runs it backwards: pick the average you want and the price you'd buy at, and it tells you the shares and the cash it would take. Sometimes the honest answer is “more than you have”.

Questions

How do you calculate the average cost of a stock?
Total spent divided by total shares. 100 shares at $50 plus 100 at $30 is $8,000 for 200 shares: $40 a share. Add your fees to the price paid if you want them counted.
How many shares do I need to buy to lower my average?
Shares = (what you've spent − target average × shares you hold) ÷ (target average − the price you'd buy at). The target has to sit between that price and your current average; anywhere else, no amount of buying gets you there, and the calculator says so.
Is averaging down a good idea?
The calculator can't tell you, and neither can anyone who doesn't know why the price fell. It shows what a buy does to your breakeven and to how much you have riding on one company. Whether the company deserves more of your money is a separate question.
Where does the stock price come from?
Type any price, or load a ticker's latest official end-of-day close. Your buys stay in your browser; nothing about your position is saved.

Educational only, not investment advice or a recommendation to buy or sell anything. Prices are official end-of-day closes. AlgoThesis is a publisher, not an adviser; see the disclaimer.Prices: Data provided by Databento (end of day)