About the Stock Average Calculator
When you buy the same stock more than once at different prices, your break-even is the weighted average cost per share, not the price of your last purchase. This stock average calculator adds up to four purchases, returns the average price, total shares and total cost, and compares them with the current market price to show your unrealised gain or loss.
It is especially useful when averaging down (buying more after a fall) or averaging up. Enter a target average and the calculator tells you how many more shares you would need to buy at the current price to bring your average down to that level, so you can judge whether the extra capital is worth committing.
Leave unused rows at zero. The same math works for ETFs, mutual fund units and crypto. Commissions are not included; if you pay them, add the fee to the purchase price or use a slightly higher price.
With the default inputs, the average price per share is $46.67. Change any value above to recalculate instantly.
How to use the stock average calculator
- 1Enter the number of shares and price for each purchase (leave unused rows at 0).
- 2Enter the stock’s current market price.
- 3Read your average cost per share and unrealised gain or loss.
- 4Optionally enter a target average to see how many more shares you would need to buy.
Formula and method
Your average cost is a weighted average: multiply the shares in each purchase by the price paid, add those amounts to get the total cost, and divide by the total number of shares. Larger purchases pull the average toward their price more than small ones.
To reach a target average T by buying at the current price P, the new total cost divided by the new share count must equal T: (N × A + x × P) ÷ (N + x) = T. Solving for x gives x = N × (A − T) ÷ (T − P), rounded up to a whole share. This only has a solution when T lies between P and your current average A.
- N
- Shares currently held
- A
- Current average price per share
- T
- Target average price
- P
- Current market price for the new purchase
Worked examples
Averaging down: 100 @ $50 then 50 @ $40
100 × $50 + 50 × $40 = $7,000 for 150 shares, an average of $46.67. At $42 the position is worth $6,300, a $700 (10%) loss. To pull the average down to $45 you would need 150 × 1.6667 ÷ 3 ≈ 83.3, so 84 more shares at $42.
Three buys on the way down
Buying 10, 15 and 25 shares at $180, $150 and $120 costs $7,050 for 50 shares, an average of $141. At $130 you are down $550, or about 7.8%.
How many shares to reach a $20 average
Your 200 shares cost $4,215, an average of $21.075. Getting to $20 by buying at $19 needs 200 × 1.075 ÷ 1 = 215 more shares, costing $4,085 — roughly doubling the position.
Frequently asked questions
How do I calculate my average stock price?+
Multiply the number of shares in each purchase by its price, add the results together, then divide by the total number of shares. For example 100 shares at $50 and 50 at $40 cost $7,000 for 150 shares, an average of $46.67.
Is averaging down a good idea?+
Averaging down lowers your break-even price but increases your exposure to a stock that has already fallen. It makes sense only if your reason for owning the company is intact; otherwise you may be adding to a losing position.
Should I include brokerage fees in the average?+
For tax cost basis in most countries, purchase fees are added to the cost. Add each fee to that purchase’s total cost (or raise the price slightly) to get a fee-inclusive average.
Does selling shares change my average cost?+
Under the average-cost method, selling part of a position does not change the average cost of the shares that remain; only new purchases do. Tax rules such as FIFO may assign a different cost to the shares you sold.
Why can’t the calculator reach my target average?+
Buying at the current price can only move your average toward that price. If your target is below the current price (when averaging down), no number of extra shares will get you there.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.