Position Sizing Explained
Position sizing turns a fixed dollar risk into the correct trade size using your stop distance. It is the single most important habit in risk management.
Size from the stop, never a fixed lot
A fixed lot size risks wildly different amounts depending on how far your stop is. Correct sizing flips it around: decide the dollars you will risk first, then let the stop distance dictate the size. Formula: size = (account × risk%) ÷ (stop distance × value per point).
Example: a $10,000 account risking 1% ($100) with a 25-point stop on an instrument worth $1/point means size = 100 ÷ (25 × 1) = 4 units. Widen the stop and the size shrinks automatically, keeping the dollar risk constant.
Why it matters
Constant per-trade risk is what makes risk of ruin calculable and small, and it is exactly what prop-firm drawdown rules force. It also removes emotion: the math sets the size, not how confident you feel.
Autonomous desks compute this mechanically before every order — no fixed lots, no discretion in the sizing step. That is the standard retail traders should hold themselves to as well.
See it live in Chart Bound
Chart Bound is our free game that trains exactly this — reading real charts one level at a time, with instant feedback. The fastest way to make position sizing click. No card, no catch.
Play Chart Bound free → Try today's Call the Candle →Frequently asked questions
How do I calculate position size?
Position size = (account equity × risk percent) ÷ (stop distance × value per point). Decide your dollar risk first, then let stop distance set the size.
Should I use a fixed lot size?
No. A fixed lot risks different dollar amounts on every trade depending on stop distance. Size from your stop so per-trade risk stays constant.
What risk percent should I size to?
Commonly 0.5% to 2% of equity per trade. Lower, constant risk keeps risk of ruin small and satisfies most prop-firm risk limits.