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Stock Average Calculator and Average Down Calculator

By Katie, author of Katie TutorialsKatieTrader and educator · 7+ yearsKatie has traded short-term options for more than seven years and teaches 300,000+ subscribers on YouTube. Every lesson here comes from her own trading journal, mistakes included.Full bioNo signals, no paid mentoring. How the lessons are kept honest · Free tool · Reviewed October 13, 2026

Bought the same stock more than once, at different prices? Enter each purchase and the calculator shows your average price per share. The second calculator shows how many shares you would need to buy to bring the average down to a price you choose. Both work for crypto too.

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Your average price

$40.00

Contents (11)
  1. Average down calculator
  2. How to use the stock average calculator
  3. How to calculate your average stock price
  4. The average down formula
  5. How fast averaging down gets expensive
  6. Should you average down?
  7. Do fees change your average price?
  8. Common mistakes
  9. Frequently asked questions
  10. Related calculators
  11. Learn it properly

Average down calculator

You own a stock that has fallen and want to know how many more shares it takes to bring your average down to a certain price. Enter what you own, the price now and the average you want.

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$
$

Shares to buy

100 shares

How to use the stock average calculator

  1. Enter the number of shares and the price for your first purchase.
  2. Do the same for every other purchase of the same stock. Use “Add a purchase” for more rows.
  3. Optional: enter the current price to see your profit or loss.
  4. To plan the next purchase, use the average down calculator above.

How to calculate your average stock price

average price = total money paid ÷ total shares

Say you bought 100 shares at 42 dollars and later 50 shares at 36 dollars. You paid 4,200 + 1,800 = 6,000 dollars for 150 shares. 6,000 ÷ 150 = 40 dollars per share.

Note that it is not simply the average of the two prices, which would be 39. The purchase with more shares counts more.

The average down formula

shares to buy = shares you own × (your average − target) ÷ (target − current price)

You own 100 shares at an average of 50 dollars. The stock is now at 40, and you want an average of 45. 100 × (50 − 45) ÷ (45 − 40) = 100 shares, which cost 4,000 dollars.

How fast averaging down gets expensive

Same position, 100 shares at 50 dollars, buying more at 40:

Target averageShares to buyCostTotal shares
$4825$1,000125
$4743$1,720143
$45100$4,000200
$43234$9,360334
$42400$16,000500

The closer the target gets to the current price, the more shares you need. Going from 45 to 42 costs four times as much as going from 50 to 45. That is why averaging down needs a plan, not a feeling.

Should you average down?

Averaging down can make sense for a long-term investor who still believes in the company and bought it for reasons that have not changed. It lowers the price the stock has to reach for the whole position to be in profit.

It is risky when it is used to avoid admitting a mistake. A stock that has fallen can keep falling, and every new purchase puts more money on the same bet. For short-term traders it is usually a bad idea: a trade has a stop, and adding to a losing trade moves the risk far past what you planned.

  • Decide before you buy the first share whether you will ever add more, and at what price.
  • Set a maximum for the whole position, and never go past it.
  • Ask yourself: would I buy this stock today, at this price, if I did not own it?

Do fees change your average price?

Yes, a little. If you want the exact number, add the commission to the price of each purchase. For 100 shares at 42 dollars with a 5 dollar commission, enter 42.05 as the price.

Common mistakes

  • Taking the simple average of the prices. It ignores how many shares each purchase had.
  • Averaging down with no limit. Each step costs more than the last, as the table shows.
  • Treating a lower average as a win. You are still down until the price comes back.
  • Averaging down in a trade instead of an investment. A trade with a stop should not grow when it goes against you.

Frequently asked questions

How do you calculate the average price of a stock?

Add up the money you paid for every purchase and divide it by the total number of shares. 100 shares at 42 dollars and 50 at 36 dollars: 6,000 ÷ 150 = 40 dollars.

How many shares do I need to buy to lower my average?

Use: shares you own × (average − target) ÷ (target − current price). With 100 shares at 50, a price of 40 and a target of 45: 100 × 5 ÷ 5 = 100 shares.

Is averaging down a good strategy?

Sometimes, for long-term investors who still believe in the company and have a limit. It is a bad habit when it is used to avoid taking a loss, and for short-term traders it usually turns a small loss into a big one.

What is averaging up?

Buying more of a stock that is rising. Your average price goes up, but you add to a position that is already working.

What is the 7% rule in stocks?

It is a rule some investors use: sell a stock if it falls 7% to 8% below what you paid, to keep losses small. It comes from the investor William O'Neil, and it is the opposite of averaging down.

Does selling shares change my average price?

With the average cost method most apps use, no. Selling part of a position does not change the average price of the shares you keep. Tax rules in your country may count it differently.

Learn it properly

  1. 1When to Exit a TradePlanning the exit before the entry, so a loss stays small.
  2. 2What Economic Factors Affect Stock Prices?Why a stock falls, and whether the reason has changed.
  3. 3How to Manage Risk in TradingHow big a position should be in the first place.

For education only, not financial advice. Trading carries a real risk of losing money. Nothing you enter is saved or sent anywhere: the calculator runs in your browser.