Stock Average Calculator
Calculate your average buy price across several share purchases, unrealised profit or loss, and how many shares to buy to reach a target average.
Tool guide
What this tool does
The Stock Average Calculator finds the weighted average cost of shares bought in several lots, including brokerage and charges. Enter the current price to see unrealised profit or loss, and set a target average to find how many more shares you would need to buy at a given price.
When you buy the same share several times at different prices, your real cost is the weighted average price, not the simple average of the prices. Buying 50 shares at 1,200, 30 at 1,050 and 20 at 980 gives an average of 1,111, because the larger lot bought at the higher price carries more weight. This figure is your break-even point and is used to work out profit, loss and, in many countries, capital gains.
The calculator divides the total amount paid, including any per-trade charges, by the total number of shares. It shows the running average after each purchase and, if you enter the market price, the unrealised gain or loss. For averaging down or up it solves shares needed = held × (average − target) ÷ (target − new price), and warns you when the target cannot be reached at the price you entered.
How to use Stock Average Calculator
- Choose the currency.
- Enter each purchase on its own line as quantity then price, for example 50 1200.
- Enter brokerage and charges per purchase if you want them included in the average.
- Enter the current market price to see unrealised profit or loss.
- Optionally enter a target average and the price of your next purchase.
- Read the average price, totals and the shares needed, and check the running-average table.
Tips for better results
- Averaging down only makes sense if your reasons for owning the stock still hold.
- Set a maximum position size before you start buying more of a falling share.
- Include charges such as brokerage, exchange fees and stamp duty for a true cost basis.
- Bonus shares and splits change the quantity; adjust older lots so prices are comparable.
Common use cases
- Tracking the cost of a share bought through several orders.
- Planning how many shares to buy to lower your average.
- Checking a broker’s average price against your own records.
- Working out the break-even price before setting a stop-loss or target.
Common mistakes to avoid
- Taking the simple average of prices instead of weighting by quantity.
- Averaging down repeatedly into a stock with deteriorating fundamentals.
- Forgetting that a lower average does not recover the money already lost.
Frequently asked questions
How is the average share price calculated?
Add up quantity × price for every purchase, plus charges, and divide by the total number of shares. The result is the weighted average buy price.
How many shares do I need to buy to lower my average?
Shares needed = shares held × (current average − target average) ÷ (target average − new purchase price). The new price must be below the target to average down.
Can I include brokerage?
Yes. Enter the charges per purchase and they are added to the cost of each lot, raising the average slightly.
Does selling shares change the average?
Under the usual average-cost method, selling reduces the quantity but leaves the average price of the remaining shares unchanged. Tax rules may use first-in, first-out instead.
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