Position size calculator
This turns an account, a risk percent, and a stop into a whole-share count, then caps that count at cash divided by the entry. Leave cash blank to use the account size. The dollar risk is the scenario on the sized shares. A stop order can fill somewhere else. The position size guide uses the same examples.
Risk-only shares = (account size × risk percent) ÷ (entry price − stop price), rounded down. Cash capacity before fees = cash ÷ entry, rounded down. Sized shares = the smaller of those two
Sized shares
Enter the account, risk percent, entry, and stop. Cash is optional.
How to size a position from a stop
- Enter the account and the risk percent. Risk percent is the fraction of the account you are measuring this scenario against. 2 means 2% of the account.
- Enter cash, the entry, and the stop. Leave cash blank to use the account size. Type a stop price, a percent below the entry, or dollars per share below the entry. The stop has to sit below the entry. Cash capacity ignores fees.
- Compare risk-only shares with cash capacity. Sized shares are the smaller whole-share count. An optional target shows planned profit on those sized shares divided by the scenario loss. The ratio does not say how often the target is reached.
Frequently asked questions
- How do you size a position from a risk limit?
- Multiply the account by the risk percent to get a dollar budget. Divide that budget by the gap between the entry and the stop, then round down. That is the risk-only share count. Cash capacity before fees is cash divided by the entry, rounded down. Sized shares are the smaller of those two. A $25,000 account risking 2% has a $500 budget. A $50 entry and a $47 stop is $3 a share, so risk-only and sized shares are both 166. Cash could fund 500 shares, so the risk budget is the constraint.
- What if the stop is so tight that the risk formula wants more shares than cash can buy?
- The calculator still reports the risk-only count, then caps the result at cash divided by the entry. $25,000, 2% risk, a $50 entry, and a $49.99 stop is 50,000 risk-only shares and a $2.5 million notional. Cash capacity is 500 shares before fees. Sized shares are 500. That is 1× cash, not 100× leverage. This cash mode does not borrow.
- Does this limit the loss if the price gaps through the stop?
- No. The dollar risk uses the stop price you type, on the sized share count. A stop order can fill at a different price, and a halt or a gap can skip the stop. The share count is the size that fits the scenario, not a cap on the loss.
- Is this investment advice?
- No. The calculator is for general informational and educational purposes only. It does not recommend a risk percent, a stop, or a trade.
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