Stock Calculator

How to use this stock profit calculator

What this calculator does

This calculator estimates the economics of one buy-and-sell stock transaction. It combines the share quantity, purchase price, purchase commission, sale price, and percentage selling commission to calculate your cost basis, net sale proceeds, profit or loss, return on investment, break-even selling price, and result per share. It is useful for comparing a planned exit price with your true transaction cost, checking whether fees materially change a small trade, and documenting a completed trade. It is not a forecast of future prices, a tax return calculation, or a recommendation to buy or sell a security.

When to use it

• Before placing a sale order, to estimate the minimum price needed to cover buying and selling costs.
• After a sale, to reconcile gross price movement with net profit after commissions.
• When comparing brokers or order sizes, to see how fixed and percentage fees affect ROI.
• When preparing a simple investment record for discussion with a financial or tax professional.

How to calculate

1. The calculator opens with a complete demonstration trade, so the results and a validated example XLSX workbook are available immediately.
2. Replace Number of shares, Buying price, Buying commission, Selling price, and Selling commission with your own figures. Use a period as the decimal separator; commas may be used only as standard thousands separators.
3. Read Profit first, then use Return on investment (ROI) and Share result to compare trades of different sizes. Check Break-even selling price before interpreting a planned sale as profitable.
4. Select Download Excel to export the current typed inputs and calculated outputs. Reset clears the demonstration values and results; the export button then stays disabled until a complete valid trade is entered again.

Input guide

Number of shares is required and accepts a positive number, including fractional shares such as 40 or 12.5. Increasing it scales gross purchase value, gross sale value, and most dollar results, while a fixed buying commission becomes less significant per share. Zero, negative values, scientific notation, and ambiguous comma decimals are rejected.

Buying price is the required U.S.-dollar price paid for each share, such as 125.00. A higher buying price raises cost basis, lowers profit and ROI for the same selling price, and raises the break-even price. Enter the trade price, not the total cash paid.

Buying commission is the required nonnegative fixed dollar cost of the purchase, such as 7.95. It is added to share cost when calculating cost basis. Enter zero when no purchase commission applied; do not enter a percentage in this field.

Selling price is the required nonnegative dollar price received or expected per share, such as 155.00. Raising it increases gross proceeds, selling commission dollars, net proceeds, profit, and ROI. A zero selling price is valid for loss analysis, but it normally produces a full-loss result.

Selling commission is the required percentage of gross sale proceeds, such as 1.00%. It must be at least 0% and below 100%. Raising it reduces net proceeds and profit while increasing the break-even selling price. Enter 1 for 1%, not 0.01. FINRA explains that transaction costs can include commissions and other charges in its guide to fees and commissions.

Output guide

Profit is net sale proceeds minus cost basis, shown in dollars. A positive value is an estimated gain, zero is break-even, and a negative value is an estimated loss. Return on investment (ROI) divides profit by cost basis and expresses the result as a percentage; it is a transaction return, not an annualized return. Break-even selling price is the per-share price that makes net proceeds equal cost basis under the stated selling commission. Share result divides total profit by shares, so it includes the per-share effect of both fees. Selling commission amount converts the entered selling percentage into dollars.

The summary pills show Cost basis, Net proceeds, and ROI. In the transaction table, Share value is price multiplied by shares, Commission is the fee at each stage, and Net amount is the cash basis or proceeds after the applicable fee. FINRA's explanation of cost basis basics provides useful context, although tax cost basis can involve adjustments beyond this calculator.

Worked example

The startup example buys 40 shares at $125.00, so the shares cost $5,000.00. Adding the $7.95 buying commission produces a cost basis of $5,007.95. Selling 40 shares at $155.00 creates $6,200.00 of gross proceeds. A 1.00% selling commission is $62.00, leaving $6,138.00 of net proceeds. Profit is therefore $6,138.00 minus $5,007.95, or $1,130.05. ROI is $1,130.05 divided by $5,007.95, or 22.56%. The break-even price is approximately $126.46 per share because the sale must cover both the original cost basis and the percentage sale fee.

Formula and interpretation

Profit = (selling price × shares × (1 – selling commission rate)) – (buying price × shares + buying commission)

Fees matter most when the trade is small, the expected price move is narrow, or commissions are high. Investor.gov's bulletin on how fees and expenses affect a portfolio explains why apparently small charges can reduce returns. For broader context on stock ownership and capital gains, see FINRA's overview of stocks.

This calculator is an educational estimate. It excludes taxes, wash-sale rules, dividends, spreads, market impact, settlement timing, foreign-exchange effects, margin interest, and broker-specific charges. Confirm actual figures with trade confirmations and qualified professionals.