Position size calculator
Work out the share count that keeps a single trade inside a fixed percentage of your account if the exit level is reached. The arithmetic is shares = (account × risk %) ÷ (entry − exit level), worked through in the position sizing article.
Reading the result
The size falls out of two numbers you choose in advance: how much of the account one idea is allowed to cost, and how far away the level is where you would admit the idea was wrong. A wider gap between entry and exit means a smaller position, not a bigger loss. That is the whole point of sizing from risk instead of from conviction.
Watch the position value line. A 1% account risk with a tight exit can produce a position worth more than the account, which only a margin account could hold, and margin brings its own trigger — see the margin call calculator.
Assumptions
- The exit fills at the level you typed. In fast markets it does not; the gap between the level and the fill is slippage.
- Whole shares only, rounded down. Fractional-share accounts can size exactly.
- One position at a time. Several correlated positions add up to one larger bet — see diversification limits.
- Illustration only, not advice. See the disclaimer.