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Enter each share purchase to instantly see your weighted average cost per share, total units held, and total amount invested across all buys. Free, no signup.
Average cost per share is the total amount invested divided by the total shares owned. This gives more weight to the larger purchases. Buying 100 shares at $50 and 300 shares at $30 costs $14,000 for 400 shares, so the average is $35. Simply averaging the two prices would incorrectly give $40. The free StockEducation Average Price Calculator totals the shares, money invested and average cost as each purchase is added. Include brokerage, currency changes and relevant tax adjustments separately when working out the official cost basis.
Enter each purchase below to calculate your average price per share across all buys.
General education only — check the assumptions before using the result.
Purpose: This calculator is a general educational tool that performs a numerical calculation from the values you enter. It does not recommend, advertise or promote a specific financial product.
Assumptions: The calculation uses the input values and assumptions displayed in the calculator. Default values are illustrative starting points, not forecasts. Change each non-statutory assumption so it matches the scenario you want to test.
Limitations: Actual market returns, prices, dividends, interest rates, fees, tax, inflation and timing may differ from the assumptions. The calculator may omit factors relevant to you. Small input changes can materially change the result, so the output is an illustration rather than a prediction.
This financial calculator is not intended to be relied on for the purposes of making a decision in relation to a financial product. You should consider obtaining advice from a financial services licensee before making any financial decisions.
You can print this page or save it electronically using your browser controls. See ASIC Instrument 2026/41 for the conditions applying to generic financial calculators.
Disclaimer · Terms of Use
Educational content only. This calculator uses the weighted average cost method. Results are for informational purposes only and do not constitute investment or tax advice. Always verify your cost basis with your broker before making any financial or tax-related decision.
100 shares bought at $10 and 100 shares bought at $20 give a weighted average price of $15 per share. The average price calculator multiplies each purchase by its share count, sums the totals, then divides by total shares held. It is the standard way to track cost basis when you buy a stock across multiple dates.
Weighted average cost across multiple buys in three steps.
Enter the number of shares and the price you paid per share for each separate buy. Add as many rows as you have purchases.
The calculator multiplies each row, sums total cost and total shares, and divides to give your true cost basis per share.
The result panel shows three values: Average Price (your true cost basis per share), Total Shares (your full position size), and Total Cost (total invested). The Average Price is what matters for capital gains tax, position sizing, and judging unrealised gain or loss against the current market price.
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Specific outcomes, not generic claims.
Simple averaging across prices ignores how many shares you bought at each. Weighted average gives the cost number that actually drives your tax and profit calculations.
Knowing your weighted average tells you how much a new buy at today’s price will move your cost basis up or down. Useful for dollar cost averaging decisions.
When you eventually sell, the weighted average is the standard cost basis method recognised in most jurisdictions for capital gains reporting.
Most calculators hide the formula. We show it because understanding the math is the point.
The weighted average price formula. Each purchase contributes in proportion to the number of shares bought.
Shares
Price
Sum
Total Shares
The projection is a mathematical model, not a forecast. Six assumptions baked into the math, plus what real outcomes look like.
Each card pairs an assumption the calculator makes with what real world investing actually looks like.
Reality: The calculator handles purchases. For partial sells, your remaining cost basis depends on whether you use FIFO, LIFO or average method.
Reality: Brokerage fees and stamp duty add to cost basis. Add them in or treat the input price as already including fees.
Reality: Multi currency purchases need conversion to one currency at the transaction date rate before averaging.
Reality: Splits, consolidations and reinvested dividends change effective share counts and cost basis. Adjust manually.
Reality: Each calculation is one ticker. Run separately for each holding.
Reality: Average price does not reflect current market value. Multiply by today’s price for current portfolio value.
Same base scenario, one variable changed at a time. The projection is highly sensitive to small changes.
The calculator assumes a smooth return every year. Here is how that compares to verified historical data.
Written by Dr. Charles Lo, Associate Professor, CPA. Reviewed annually.
Weighted average price is your true cost basis when you have bought the same stock multiple times at different prices. It is calculated by multiplying each purchase by its share count, summing the totals, and dividing by total shares held.
A common mistake is averaging the prices directly. If you bought 1,000 shares at $20 and 100 shares at $30, the simple average of $25 is wrong. The weighted average is $20.91 because most of your shares were bought at the lower price.
Weighted average matters most when you sell. It determines your capital gain or loss and therefore the tax you owe. It also tells you how much of a margin of safety you have against the current price before a paper loss becomes real.
Always include brokerage fees and any stamp duty in your effective price per share. A $10 stock with a $5 brokerage fee on 100 shares has an effective per share cost of $10.05.
When using dollar cost averaging, your weighted average will land between the highest and lowest prices you paid, weighted toward periods when shares were cheaper (because the fixed dollar bought more).
Compare your average price to the current market price. If current is higher, you have an unrealised gain. If lower, an unrealised paper loss. Neither becomes real until you sell.
Compare your average to recent purchase prices. If your average is much lower than today’s price, you have a sizeable cushion. If your average is close to or above today’s price, a small further drop will put you in loss territory.
Real numbers calculated from the same formula as the live tool. Every figure below is verified, not approximated.
100 shares at $20, then 100 shares at $10
An investor bought half their position before a market drop, then added the other half at the lower price.
1,000 shares at $20, then 100 shares at $30
An investor built a meaningful position early, then added a small amount later at a higher price after good news.
100 at $25.50, 150 at $28, 200 at $22.75, 50 at $35
A planner spreads buys across a year to smooth out volatility. Different share counts at each price reflect changing conviction.
$1,000 monthly for 3 months, prices $10, $9, $11
An investor commits a fixed dollar amount each month regardless of price. The fixed dollar buys more shares when price is low.
100 shares at $50 plus $9.95 brokerage
A single buy of $5,000 attracts a flat brokerage fee. The fee adds to cost basis.
The questions users most often ask about calculator output.
Yes. The calculator is free to use, no signup or account required. It runs in your browser. Your inputs are not stored or shared.
Simple average adds prices and divides by count. Weighted average multiplies each price by share count first. Weighted average is correct for cost basis because it reflects how many shares you actually bought at each price.
Yes. Brokerage fees and stamp duty add to cost basis. Either include them in the price per share you enter, or compute the effective price per share separately and use that figure.
The calculator only handles buys. After a sell, your remaining cost basis depends on whether you use FIFO, LIFO, average method or specific identification. Check with your broker which method applies.
After a 2 for 1 split, double your share count and halve your average price. The total cost basis is unchanged. Reverse the adjustment for reverse splits or consolidations.
Not automatically. DRIP shares are additional buys at the reinvestment date price. Add each DRIP as a new purchase row to keep your average correct.
Yes. The math is identical for any pooled investment unit. Use the units bought and the price per unit you paid.
Weighted average price per share is one cost basis method. The other common methods are FIFO, LIFO, and specific identification. Your tax outcome can differ based on which method is allowed and which you elect.
Other tools for different parts of your financial picture.
The calculator uses the weighted average cost basis formula, which is the standard cost basis method recognised by major tax authorities including the ATO and the IRS.
This calculator is provided for general educational purposes only. It does not constitute financial or tax advice and does not take into account your personal objectives, financial situation or needs. Cost basis methods vary by jurisdiction and account type. Consult a registered tax agent or accountant for your specific reporting obligations.
This calculator gives you the number. Our free courses teach you the why behind the math, the assumptions to question, and how to apply it to your own portfolio.
Add each purchase row to see your weighted average cost per share, total units held, and total amount invested across all buys.
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