About the Stock Average Calculator
Averaging down means buying more shares after the price falls to lower your average cost per share; averaging up means adding to a winner. This calculator combines several buys at different prices, shows your new average cost, and – if you enter the current price – compares your return before and after the extra purchases.
Fractional shares are supported, and your inputs are saved only in this browser.
How to use
- Enter the average price and number of shares you own now.
- Enter the price and quantity of each additional buy. Tap + Add a buy for more lots.
- Optionally enter the current price to see market value, unrealized gain/loss and the return before and after.
- In the last box, enter a target average and a buy price to see how many shares you’d need.
Average cost formula
New average = (current average × current shares + price₁ × shares₁ + price₂ × shares₂ …) ÷ total shares
Example: you own 100 shares at $50 and buy 50 more at $40. Your new average is ($5,000 + $2,000) ÷ 150 = $46.6667 (about $46.67).
To reach a target average: shares needed = shares owned × (current average − target) ÷ (target − buy price), rounded up. In the example, getting to a $45 average at a $40 buy price takes 100 × 5 ÷ 5 = 100 shares.
Before you average down
- A lower average doesn’t reduce your loss in dollars – you simply have more money in the same stock, so a further drop hurts more.
- It only lowers your break-even price. Commissions, spreads and taxes are not included.
- The closer the target average is to the buy price, the more shares you need; the number can explode.
- For taxes, your broker may use FIFO or specific lots rather than the average cost, so realized gains can differ.
FAQ
What’s the difference between averaging down and averaging up?
Averaging down is buying below your average price to lower it; averaging up is buying above it to add to a rising position. The formula is the same.
Why does the target calculation say “Not possible”?
To lower your average you have to buy below the target, and to raise it you have to buy above the target. If the buy price is equal to the target or on the wrong side of it, no number of shares will get you there.
Are fees included in the average price?
No, the calculator uses execution prices only. If you want fees in your cost basis, add the commission per share to each buy price.
Does it work with fractional shares?
Yes. Enter quantities like 0.5 or 2.25 shares; averages are shown to four decimal places.