Stock Average Calculator (Average Down)
Type in each buy (shares and price per share) to get your average cost, total invested, and the move needed to break even from today's price. Add a planned purchase to preview your new average before you place the order.
Lot 1
Lot 2
Lot 3 (optional)
Lot 4 (optional)
Planned purchase (optional)
Used for the break-even move
Total shares
20
across 2 lots
Average cost per share
$45.00
total invested divided by total shares
Total invested
$900
New average with planned buy
—
Fill in the planned purchase to preview it
Move to break even
+7.1%
the price must rise from $42.00 to $45.00
Position breakdown
| Lot | Shares | Price | Cost | Share of position |
|---|---|---|---|---|
| Lot 1 | 10 | $50.00 | $500 | 56% |
| Lot 2 | 10 | $40.00 | $400 | 44% |
A lower average also means more dollars riding on one ticker: the break-even gets closer, the exposure gets bigger.
The formula: a weighted average, nothing fancier
Your average cost per share is total dollars in divided by total shares held. Every lot contributes its shares times its price to the top of that fraction, which is why the average always lands closer to the price of your bigger purchase. The calculator ignores any lot with a blank share count or price, so you can start with two buys and add the others as they happen. The same arithmetic runs the planned-purchase preview: it just adds one more lot to both sides of the fraction before dividing.
Averaging down in practice
Say you bought 10 shares at $50, watched the price slide, and bought 10 more at $40. You now hold 20 shares, $900 in, for an average of $45. With the stock at $42, break-even needs about a 7.1% rise instead of the 19% the first lot alone would have required. Thinking about a third buy? Enter 10 planned shares at $42 and the average drops to $44. That is the entire appeal of averaging down: each cheaper lot moves the finish line closer.
What averaging down does and does not do
The honest framing: a lower average does not recover a single dollar you have already lost, it changes the price at which future dollars break even, while committing more money to the same stock. In the example above, the position grew from $500 at risk to $900, and a further slide now hurts nearly twice as fast. That concentration is the real cost, and it is why diversification exists as a concept. There is also a disciplined cousin: dollar-cost averaging buys on a schedule regardless of price, which builds an average without the temptation to double up only on losers. This page computes either one; it has no opinion on which stock deserves your next dollar, and neither should a calculator.
Your average follows you to the sale
When you eventually sell, the tax math runs on your cost basis: proceeds minus what you paid determines the gain or loss you report, lot by lot. Brokerages let you choose which lots to sell, and the choice can change the taxable result even when the cash received is identical. Knowing your per-lot prices and your blended average, exactly what this page shows, is the groundwork for making that choice deliberately instead of accepting whatever the default picks.
Frequently asked questions
How do you calculate the average price of a stock across multiple buys?
Add up the dollars from every purchase (shares times price for each lot), then divide by the total number of shares. It is a weighted average, so a big lot moves the number more than a small one. Buying 10 shares at $50 and 10 at $40 gives an average of $45.
What does averaging down mean?
Buying more of a stock after its price has fallen below what you paid. The new, cheaper shares pull your average cost down, which lowers the price the stock must recover to before your position breaks even.
Does averaging down recover my losses faster?
It lowers the break-even price, but it does not undo the loss on the shares you already own, and it puts more money into the same stock. If the price keeps falling, you lose more than you would have. It is a bet sized up, not a loss erased.
What is cost basis and why does it matter?
Cost basis is what you paid for your shares, including each lot's price. When you sell, your taxable gain or loss is the sale proceeds minus that basis, so keeping accurate lot records matters at tax time. Brokerages track it, but knowing your own average helps you sanity-check their numbers.
Can I use this for ETFs, mutual funds, or crypto?
Yes. The math is the same for anything bought in units at a price: ETFs, mutual funds, or coins. Fractional shares work too, just type the decimal.
Does this calculator save my numbers?
No. Everything runs in your browser and nothing you type is stored or sent anywhere.
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