Position Size Calculator
Decide how many shares to buy from your account size, risk per trade and stop-loss level.
About the Position Size Calculator
Enter your account size, the percentage you're willing to lose on one trade, your entry price and your stop-loss price. The calculator gives the number of shares, the amount at risk and how much of the account the position uses.
Position sizing keeps any one losing trade to a small, fixed share of your account, commonly 1–2%. The distance to your stop-loss sets how many shares that risk allows: a tighter stop allows more shares, a wider stop fewer.
The formula
Shares = (account × risk %) ÷ |entry − stop|
- account × risk %
- the most you're prepared to lose on this trade
- |entry − stop|
- the loss per share if the stop is hit
Worked example
A 25,000 account risking 1%, entry 50, stop 47
- Risk: 25,000 × 1% = 250
- Loss per share at the stop: 50 − 47 = 3
- Shares = 250 ÷ 3 = 83 (rounded down), a 4,150 position, 16.6% of the account
Things to keep in mind
- Fees and slippage are not included; they make a real loss slightly larger.
- For short trades the stop is above the entry; the calculator uses the distance either way.
Questions people ask
Does the stop guarantee my loss?
No; prices can gap past a stop, especially overnight.
Why 1%?
It lets you survive long losing streaks: ten losses in a row cost under 10% of the account.
Why are shares rounded down?
Rounding up would risk slightly more than your limit.