The stock calculator estimates the outcome of one purchase and one sale of the same number of shares. It combines purchase cost, sale proceeds, separate commissions, and a user-entered capital-gains-tax rate. Results include per-share net prices, total investment, gross profit or loss, estimated tax on a positive gain, net profit or loss, and a commission-adjusted break-even sale price. It is a planning worksheet, not a tax return or investment recommendation. Actual tax treatment depends on jurisdiction, holding period, account type, cost-basis rules, and personal circumstances.
Stock Calculator
Stock Form
Results
Net Buy Price
$0.00
Buy Commission
$0.00
Net Sell Price
$0.00
Sell Commission
$0.00
Break-Even Share Price
$0.00
Profit/Loss
$0.00
Table of Contents
1
What is Stock Calculator ?
2
How to Use This Calculator
- Enter the number of shares. Fractional shares are accepted, but the value must be greater than zero.
- Enter purchase and proposed sale prices per share in the same currency.
- Enter the tax rate as a percentage, such as 20 for 20%, not 0.20.
- Enter total buy and sell commissions for the whole trade. Use zero where no commission applies.
- Choose Calculate and review the gross result before tax, the tax estimate, and the net result.
Keep every money input in one currency. The worksheet applies the entered tax rate only when its computed gross result is positive. It does not model tax brackets, holding-period rates, loss offsets, wash-sale rules, currency conversion, dividends, spread, or fees other than the two commissions.
3
Formula Used
Net buy price per share = purchase price + buy commission ÷ shares
Net sell price per share = sale price − sell commission ÷ shares
Total investment = purchase price × shares + buy commission
Total sale value = sale price × shares − sell commission
Gross profit/loss = total sale value − total investment
Estimated tax = positive gross profit × tax rate ÷ 100
Net profit/loss = gross profit/loss − estimated tax
Break-even sale price = (purchase cost + both commissions) ÷ shares
4
Variables Explained
| Value | Meaning |
|---|---|
| Number of shares | Quantity bought and sold in this single scenario. |
| Purchase price | Market price paid per share before buy commission. |
| Sell price | Market price received per share before sell commission. |
| CGT rate | User-supplied percentage applied only to a calculated positive gain. |
| Buy commission | Total acquisition charge included in investment cost. |
| Sell commission | Total disposal charge deducted from proceeds. |
| Break-even price | Per-share sale price that covers purchase cost and both entered commissions before tax. |
5
Worked Example
Suppose 100 shares are bought at $20 and sold at $25. Buy commission is $10, sell commission is $15, and the tax-rate assumption is 20%. Total investment is $2,000 + $10 = $2,010. Net sale value is $2,500 − $15 = $2,485. Gross profit is $475. Estimated tax is $475 × 20% = $95, leaving $380 net profit. Net buy and sell prices are $20.10 and $24.85 per share. Break-even is ($2,000 + $10 + $15) ÷ 100 = $20.25 per share.
6
Why Use This Calculator?
A positive net figure means the assumed sale proceeds exceed entered costs and the simple tax estimate. A negative figure means a loss under those inputs; the calculator does not turn that loss into a tax benefit. Break-even covers both entered commissions but no tax, bid-ask spread, market impact, exchange fees, or other charges.
Use the result to compare clearly stated scenarios, such as two possible sale prices or fee schedules. Do not infer that a profitable scenario predicts the market. For tax records, use broker confirmations and the cost-basis method allowed in your jurisdiction. In the United States, the IRS generally includes acquisition costs in basis and has specific identification and default rules for sold shares. Consult a qualified tax professional where the treatment is material or unclear.
7
Common Mistakes
- Entering the tax rate as 0.20 when you mean 20% produces a rate one hundred times smaller.
- Entering per-share commission instead of the total commission counts the fee incorrectly.
- Mixing currencies makes every total and comparison meaningless.
- Ignoring the sell commission understates the price needed to break even.
- Treating the displayed tax as final ignores exemptions, brackets, holding periods, loss offsets, and local law.
- Using today’s quote as guaranteed sale proceeds overlooks spread and price movement.
- Calling gross profit “return” without comparing it with invested capital can misstate performance.
8
Frequently Asked Questions
Does the calculator predict a stock’s future price?
No. It evaluates the prices you enter. It does not forecast market movement, dividends, volatility, or whether buying or selling is suitable.
What should I enter for the tax rate?
Enter a percentage such as 15 or 20. Use a rate appropriate to your scenario only after checking applicable rules; the worksheet does not determine your legal rate.
Why is tax zero when the trade shows a loss?
The simplified model applies the entered rate only to a positive calculated gain. It does not estimate deductions, loss carryovers, or offsets against other gains.
Does break-even include tax?
The displayed break-even sale price covers purchase cost plus both commissions. At zero gain there is no positive gain for this tax formula, but other charges may still apply.
Can I use fractional shares?
Yes. The arithmetic accepts a positive fractional quantity. Make sure both prices and total commissions relate to that same quantity.
Are dividends included?
No. Dividend income, withholding, reinvestment, and changes to basis are outside this one-purchase, one-sale calculation.
Is commission part of cost basis?
Acquisition and disposal costs often affect gain calculations, but exact treatment depends on applicable law and transaction details. Keep broker records and check official guidance.
9
Sources & References
The IRS stock-basis FAQ explains that purchase price and acquisition costs generally form basis and describes share-identification rules. More detail appears in IRS Publication 550. The US Securities and Exchange Commission’s Investor.gov fee bulletin explains how transaction and account fees reduce investment returns. Tax rules differ by place and can change.
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