Position size calculator
The question that separates traders from gamblers: how many shares can I buy so that if my stop-loss hits, I lose exactly what I planned — and nothing more?
Educational tool, not advice. It sizes the trade you've already decided to take; it has no opinion on whether you should take it.
> if_stopped_out: lose $100.00, live to trade again
// the rule this implements
Risk a fixed slice of your account per trade — most commonly 1%, rarely more than 2%. The math: shares = (account × risk%) ÷ (entry − stop). Your position size falls out of your stop distance, not your confidence level. Tight stop, bigger size; wide stop, smaller size; same dollars at risk either way.
// why 1% matters
At 1% risk per trade, ten straight losses — a brutal streak — costs about 9.6% of your account. Annoying, survivable. At 10% risk per trade, the same streak costs ~65%. Position sizing is why some traders survive their bad months and others become cautionary tales. Related reading on the Press: what is margin and limit vs market orders.