Size a position before you enter the trade

'How much can I buy?' is the wrong question — it's 'how much can I lose?'. Risk a fixed percent and let the stop set the size.

Tools used in this guide

The job

Position sizing is the difference between a bad trade and a bad month. Decide what fraction of equity you'll risk (1% is the classic), place your stop, and the math gives you shares — not the other way around.

Five numbers in

Account equity, risk %, entry price, stop price, optional target. Out comes the risk amount, per-unit risk, the rounded-down unit count, the position's total value and share of equity.

Long and short both work — the tool detects direction from entry vs stop.
With a target set, reward:risk and the break-even win rate appear: 2:1 needs 33.3% winners to break even.

Read before you size up

The count is floored — you get whole shares/units within risk. If the result says the position is 40% of equity, the stop is tight, not safe: tight stops get wicked out. This is arithmetic, not advice.