Stock Average Calculator
Find your average cost per share across several purchases and see your gain or loss at the current price.
Free · No sign-up · Runs in your browser · Last reviewed November 2026
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Enter up to four purchases (shares and price per share):
About the Stock Average Calculator
When you buy the same stock at different prices, your average cost basis is the total money invested divided by the total shares. This stock average calculator combines up to four purchases, shows your break-even price and calculates the gain or loss at the current price. Averaging down means buying more after a price drop to lower your average cost.
How to use it
- Enter the shares and price for each purchase you made.
- Enter the current share price.
- Press Calculate average cost to see your cost basis, break-even price and profit or loss.
Average cost formula
Average cost = total amount invested ÷ total shares. Buying 100 shares at $50 and 50 shares at $40 costs $7,000 for 150 shares, an average of $46.67.
Averaging down: example
| Purchase | Shares | Price | Cost |
|---|---|---|---|
| Buy 1 | 100 | $50.00 | $5,000 |
| Buy 2 | 50 | $40.00 | $2,000 |
| Total | 150 | $46.67 average | $7,000 |
Remember
- Fees and commissions raise your real cost basis.
- Averaging down increases your exposure to a falling stock.
- For taxes, brokers track cost basis by lot, and the method you choose affects capital gains.
Averaging down: a second example and the risks
Say you bought 40 shares at $25, 60 shares at $20 and 100 shares at $15. You invested $3,700 for 200 shares, so your average cost is $18.50. If the stock now trades at $17, your position is worth $3,400 and you are down $300 (8.1%). To break even, the price must rise about 8.8% to $18.50.
Notice how the average ($18.50) sits closer to the cheaper purchases because you bought more shares at lower prices. That is the main effect of averaging down.
Things to keep in mind
- A lower average is not a lower risk. You have put more money into a stock that is still falling, and the thesis may have changed.
- Commissions and fees. Add them to your cost if your broker charges any.
- Wash sale rule. If you sell at a loss and buy the same security within 30 days before or after, the loss may be disallowed for tax purposes.
- Lots matter for taxes. Brokers report gains by lot, so the average cost may differ from the cost basis reported on your 1099-B.
Position size should reflect your overall portfolio, not just the average price.
Frequently asked questions
How do I calculate average stock price?
Add the total dollars spent on all purchases and divide by the total number of shares.
What does averaging down mean?
Buying more shares at a lower price to reduce your average cost per share.
What is cost basis?
The original price you paid for an investment, including fees, used to calculate gains and losses for taxes.
Does the average cost matter for taxes?
Brokers usually use specific methods such as FIFO or average cost for mutual funds. Check how your broker reports it.
Is averaging down a good strategy?
It depends on whether you still believe in the company. It can lower your cost but raises risk if the price keeps falling.
Is averaging down a good strategy?
It depends on why the price fell. It can make sense for a sound company at a temporary discount, but it adds risk if the business has deteriorated. Many investors set a maximum position size in advance.
What is the difference between average cost and cost basis?
Average cost is the total invested divided by total shares. For taxes, cost basis is tracked per lot and can include fees, and your broker's default method (such as FIFO or average cost for funds) determines which lots are sold.
Last reviewed: November 2026. Estimates only, not tax, legal or financial advice.