What is the Position Size Calculator?
The Position Size Calculator is a free online tool that helps you shares to buy for a fixed % account risk It runs entirely in your browser, gives an instant result, and needs no sign-up, download or spreadsheet.
Position size is the lever that decides how much a losing trade actually costs you — it's set by your account size, the percentage you're willing to risk, and the distance to your stop.
Whether you trade stocks, forex, options, crypto or futures, the position size is the same calculation — so this tool works for any market. Use it before you place a trade to base your decision on real numbers instead of a guess.
How to use the Position Size Calculator
Using the position size calculator takes only a few seconds:
- Enter your figures in the position size calculator above — the fields are filled with an example you can replace.
- Read the highlighted result; it updates instantly as you type.
- Add your broker’s fees or commissions where relevant for a true net figure.
- Change any input to compare scenarios before you commit to the trade.
Position Size formula & example
The position size formula is: Position size = (account × risk %) ÷ (entry − stop).
With a $25,000.00 account risking 2% (=$500.00), entry $100.00 and stop $90.00 (risk $10.00/share), position size = $500.00 ÷ $10.00 ≈ 50 shares.
When to use the Position Size Calculator
Reach for the position size calculator whenever you’re planning a trade and need to know your position size in advance. Running the number first keeps your decisions consistent and stops a single trade from doing outsized damage to your account. Traders who make this a habit — checking before every entry — are the ones who protect their capital over the long run.
Why use a position size calculator?
Doing position size by hand is slow and error-prone — a misplaced decimal or a forgotten fee can turn a winning plan into a losing one. The position size calculator removes that risk: it applies the correct formula every time, updates the moment you change an input, and lets you test several scenarios in seconds.
That speed matters in live markets. When a setup appears you can size it, check the reward against the risk, and act before the opportunity passes — without second-guessing your arithmetic.
- Instant, accurate position size with no spreadsheet
- Free, with no account, login or download
- Works on mobile and desktop, right in your browser
- Useful for stocks, forex, options, crypto and futures
Tips for accurate position size
- Use your real entry, exit and size — not round-number guesses.
- Include fees and spread; small costs add up across many trades.
- Recalculate whenever your price, size or stop changes.
- Round against yourself to leave a margin for slippage.