Position size & risk calculator
Decide what you’re willing to lose on this one trade (a percent of the account), then enter your entry and stop-loss — the calculator returns the whole-share count that puts your worst case right at that budget, along with position value, the actual risk after rounding to whole shares, and (when you add a target) the reward-to-risk. It works long or short; for a long, it flags when the risk-based size costs more than your cash. Every number is a disclosed division of what you typed — not investment advice.
Enter account size, risk %, entry and stop-loss to compute.
Position sizing is arithmetic on the numbers you enter — not a recommendation to take any trade, and not investment advice. It assumes your stop fills exactly at the stop price; real fills can slip past it, especially on gaps.
How the sizing works
- Risk budget = account size × risk % — the dollars you’ve decided you can lose on this trade.
- Risk per share = |entry − stop| (entry − stop for a long, stop − entry for a short); a stop on the wrong side or equal to entry is flagged.
- Shares = floor(risk budget ÷ risk per share) — rounded down to whole shares, so the actual risk at that size is always ≤ the budget, never over.
- For a long on a cash basis: if shares × entry exceeds the account, it’s flagged with the max shares your cash can buy and the risk at that size (a short needs a margin account; this is a risk calc, not a margin check).
- Reward-to-risk = reward per share ÷ risk per share (when a target is set) — a ratio, not a probability of success and not a price forecast.