You bought at one price, sold at another, and paid commission twice — so did you actually make money? The answer is less obvious than sell minus buy, because fees quietly eat into every trade.

The calculator above does the full accounting. Enter your share count, buy and sell prices, and commission per trade, and it returns your profit or loss, the return on investment as a percentage, and the breakeven sell price that would have left you exactly even.

This guide walks through each number, shows the formulas at work, and explains how to read the results before your next trade.

What Does the Position Calculator Do?

You enter four values: the number of shares, the buy price per share, the sell price per share, and the commission charged per trade. The dollar sign sits outside each money box so the inputs stay clean.

The headline announces your profit or loss in dollars. Beneath it, four labeled rows show the total purchase cost, the total sale proceeds, the return on investment as a percentage, and the breakeven sell price per share.

Commission is applied twice — once on the buy, once on the sell — because that is how brokerages actually charge. The note under the results explains that taxes and dividends are excluded, so the figures describe the trade itself, not your tax return.

How to Use the Position Calculator

Type the share count into the first box — whole shares only, starting at one. Then enter the buy price and sell price per share, and the commission your broker charges per trade, using zero if your broker is commission-free.

Press Calculate. The headline immediately tells you whether the trade made or lost money, and the rows break down exactly where every dollar went.

Press Reset to clear the form and model a different trade. Comparing the breakeven price of two candidate trades is one of the most useful things this calculator does.

Total Purchase Cost

Total purchase cost is everything the buy side took out of your pocket: shares times buy price, plus one commission charge.

The formula is:

cost = shares × buy price + commission

For 100 shares bought at $45.20 with a $4.95 commission, that is 100 × 45.20 + 4.95 = $4,524.95. Many investors forget the commission here and then wonder why their mental math never matches the brokerage statement.

Total Sale Proceeds

Total sale proceeds are what the sell side put back in your pocket: shares times sell price, minus the second commission charge.

The formula is:

proceeds = shares × sell price − commission

Selling those 100 shares at $52.75 with the same $4.95 commission gives 100 × 52.75 − 4.95 = $5,270.05. Proceeds are always slightly less than shares times price, and on small trades that slight difference matters.

Profit or Loss

Profit or loss is proceeds minus cost — the single number that decides whether the trade was worth it.

The formula is:

profit = proceeds − cost

With $5,270.05 in proceeds and $4,524.95 in cost, the profit is $745.10, and the headline reads “Profit: $745.10”. A negative result flips the headline to “Loss:” with the same arithmetic.

Return on Investment

Return on investment expresses the profit as a percentage of what you put in, which lets you compare trades of very different sizes.

The formula is:

ROI = profit ÷ cost × 100

A $745.10 profit on a $4,524.95 cost is a 16.47% return. That percentage is the number to compare against alternatives — a 16% return on a small position beats a 4% return on a large one in efficiency terms.

The Breakeven Sell Price

The breakeven sell price is the per-share price at which the trade nets exactly zero — the line between profit and loss.

The formula is:

breakeven = buy price + 2 × commission ÷ shares

With a $45.20 buy price, $4.95 commission, and 100 shares, breakeven is 45.20 + 9.90 ÷ 100 = $45.30. Anything above $45.30 per share is profit before taxes; anything below is a loss.

Worked Example: Profitable Trade

You buy 100 shares at $45.20, sell at $52.75, and pay $4.95 commission per trade.

First: enter 100, 45.20, 52.75, and 4.95, then press Calculate.

Total cost is 100 × 45.20 + 4.95 = $4,524.95. Total proceeds are 100 × 52.75 − 4.95 = $5,270.05.

Then: profit is 5,270.05 − 4,524.95 = $745.10, ROI is 745.10 ÷ 4,524.95 × 100 = 16.47%, and breakeven is $45.30.

Answer: Profit of $745.10, a 16.47% return — the trade cleared its breakeven of $45.30 by a wide margin.

Worked Example: Losing Trade

You buy 50 shares at $60.00, sell at $55.00, with zero commission.

First: enter 50, 60.00, 55.00, and 0, then press Calculate.

Total cost is 50 × 60.00 = $3,000.00. Total proceeds are 50 × 55.00 = $2,750.00.

Then: the loss is 2,750.00 − 3,000.00 = −$250.00, ROI is −250 ÷ 3,000 × 100 = −8.33%, and breakeven is $60.00.

Answer: Loss of $250.00, an −8.33% return — the sale price never reached the $60.00 breakeven.

Worked Example: Commission Changes the Verdict

You buy 10 shares at $20.00 and sell at $21.00, with a $6.95 commission per trade.

First: enter 10, 20.00, 21.00, and 6.95, then press Calculate.

Naive math says the profit is $10.00, but total cost is 200 + 6.95 = $206.95 and proceeds are 210 − 6.95 = $203.05.

Then: the real result is a loss of $3.90, because breakeven was 20.00 + 13.90 ÷ 10 = $21.39 — above the $21.00 sale price.

Answer: Loss of $3.90 — the trade looked profitable until both commissions were counted.

Why Small Trades Suffer Most From Fees

Breakeven rises as the share count falls, because the fixed commission spreads over fewer shares. With a $6.95 commission, ten shares need $1.39 per share of price gain just to break even; a hundred shares need only $0.14.

This is why the breakeven row matters more than the profit row for small accounts. A trade can show a green headline on price movement alone and still lose money after fees.

If your broker charges zero commission, enter zero and the breakeven collapses to exactly the buy price — the cleanest case the calculator handles.

A useful habit is to check the breakeven before every trade and write it on your order ticket. When the position moves against you, the breakeven is the objective line where hope ends and the loss begins — having it precomputed removes the temptation to redraw it later.

Edge Case: Selling Below the Buy Price

The calculator handles losses without complaint. Enter a sell price below the buy price and the headline switches to “Loss:” with the same four-row breakdown.

Losses still have a breakeven price, and it is still above the buy price when commission is positive. Knowing that number tells you exactly how far the price needed to recover.

The ROI goes negative in the same proportion. A −8.33% return on one trade is the figure to carry into your records, not the raw dollar loss.

Losses also have a tax dimension the calculator does not model: realized losses can offset gains elsewhere in many tax systems. The calculator tells you the size of the loss; your tax situation determines what that loss is worth to you.

Common Position Calculation Mistakes

The most common mistake is counting commission once instead of twice. Every round trip — buy plus sell — pays the fee on both ends, and the calculator’s breakeven formula uses 2 × commission for exactly this reason.

The second mistake is comparing dollar profits across different position sizes. A $745 profit on $4,525 invested and a $745 profit on $40,000 invested are very different trades; ROI is the comparison tool, not dollars.

The third mistake is forgetting that the results exclude taxes and dividends. A profitable trade can still owe short-term capital gains tax, and a dividend received during the holding period is a separate gain the calculator does not add.

Where Position Calculations Are Useful

Active traders run these numbers before entering a position, setting a mental stop at the breakeven price. If the thesis breaks below breakeven, the exit decision is already made.

Long-term investors use the calculator at tax time, verifying brokerage statements and separating the trade’s economics from the tax bill that follows.

Beginners use it to learn the true cost of trading. Running a few hypothetical small trades through the commission math is a cheap lesson compared to learning it with real money.

How to Interpret Your Result Correctly

Read the headline for the verdict, the ROI for the efficiency, and the breakeven for the lesson. A 16.47% ROI with a $45.30 breakeven says the trade worked and had room to spare.

Compare ROI across trades, never raw dollars. Percentages normalize for position size; dollars do not.

Remember the exclusions. Taxes, dividends, and the time your money was tied up all sit outside these numbers — the calculator measures the trade, and you measure everything around it.

Frequently Asked Questions

1. What is a stock position?

A position is your holding in a single stock — the number of shares you own. This calculator evaluates one completed round trip: buying the shares and later selling them.

2. Why is commission charged twice?

Brokers charge per trade, and a round trip is two trades: the buy and the sell. The calculator adds one commission to the cost and subtracts one from the proceeds.

3. What if my broker charges no commission?

Enter zero in the commission box. The breakeven price then equals the buy price exactly, and profit is simply shares times the price difference.

4. How is ROI calculated?

The formula is ROI = (proceeds − cost) ÷ cost × 100. A $745.10 profit on a $4,524.95 cost gives the 16.47% in the worked example.

5. What is the breakeven sell price?

The per-share price where profit equals zero: breakeven = buy price + 2 × commission ÷ shares. Sell above it for profit, below it for a loss.

6. Can the calculator show a loss?

Yes. When proceeds fall short of cost, the headline reads “Loss:” followed by the dollar amount, and the ROI row shows a negative percentage.

7. Does it handle fractional shares?

The share box accepts whole numbers starting at one. For fractional-share trades, scale up — for example, model 2.5 shares as 25 shares at one-tenth the prices — and read the profit and ROI normally.

8. Are dividends included?

No. The calculator measures the buy-and-sell trade only. Add any dividends received to the profit yourself if you want the full holding-period return.

9. Are taxes included?

No. Profits may be taxed as short-term or long-term capital gains depending on your holding period and jurisdiction. The calculator shows pre-tax economics.

10. Why does my profit not match my brokerage statement?

Check the commission figure first — statements sometimes bundle fees you did not model. Corporate actions like splits, which change share counts and prices, also break the simple comparison.

11. What is a good ROI for a single trade?

There is no universal target; it depends on the holding period and risk. A 16% return in a month is excellent, while the same return over five years trails the broader market.

12. Should I include the time held?

The calculator does not ask for it, but you should consider it. Annualizing the ROI — roughly dividing by years held — tells you whether the trade beat simply holding an index fund.

13. Can I model a short sale?

Not directly. The calculator assumes a standard long position: buy first, sell later. Short positions reverse the cash flows and need different math.

14. Why does breakeven exceed my buy price?

Because of the two commissions. The price must rise enough to cover both fees before the trade breaks even — $45.30 versus a $45.20 buy in the worked example.

15. Is my trade data saved anywhere?

No. All calculations run in your browser and nothing is transmitted or stored. Reset or close the page and the numbers are gone.