Position Size Calculator
R-based sizing: risk a fixed % of your account per trade. This calculator converts that risk into the exact position size in both contracts and notional USD, so you never eyeball a position again. For deeper theory see our Kelly risk guide.
Account & trade
Sizing
Position size0.10000contracts
Notional$5,000.00leverage 0.50x
Risk (R)-$100.00if stop hits
Reward+$200.00if target hits
Risk/reward1 : 2.00R multiple
EV at 50% win+$50.00expected value
How the math works
- Risk in USD = account_usd × (risk_percent / 100)
- Stop distance = |entry − stop|
- Position (contracts) = risk_usd / stop_distance (rounded down to lot size)
- Notional (USD) = position × entry
- Leverage used = notional / account
Rule of thumb: risk 0.5-1% per trade. Risking 5% means 20 losers in a row and you're down 64% · math does not care about how certain you felt going in.
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