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Trade Position Size & Risk-Reward Calculator

Size a trade from a fixed percentage of account equity you're willing to risk, and see the reward-to-risk ratio between your entry, stop-loss, and target prices.

Amount at risk
$100.00
Risk per unit (entry to stop)
$2.00
Reward per unit (entry to target)
$6.00
Reward-to-risk ratio
3 : 1
Position size (whole units)
50
Position value at entry
$2,500.00
Potential profit at target
$300.00
Potential loss at stop
$100.00

How it works

This applies the standard 'risk a fixed percentage of your account per trade' money-management rule. The dollar amount at risk is account equity × risk %. Dividing that by the per-unit risk — the distance between your entry and stop-loss price — gives the position size: how many shares or units you can hold while keeping your maximum loss at exactly your intended risk amount.

Risk and reward per unit are both measured as plain distances from the entry price (|entry − stop| and |target − entry|), so the same formulas work for a long trade (stop below entry, target above) or a short trade (stop above entry, target below) without needing a separate direction input — only the distances matter for sizing and the ratio.

The reward-to-risk ratio (reward per unit ÷ risk per unit) is a common screening filter traders use before taking a setup, independent of position size — a small account and a large account sizing the same entry/stop/target will always get the same ratio, just a different position size.

FAQ

Why use whole units for the position size but a fractional number elsewhere?

You can't buy a fractional share on most exchanges, so the position size is floored down to a whole number as the practical, tradeable answer. The other figures (position value, potential profit/loss) are shown using the exact fractional size so they stay internally consistent with each other; rounding the share count down slightly reduces the true risk below your target, never above it.

Does this account for trading fees or slippage?

No — it's the pure position-sizing formula from your stated entry, stop, and target prices. Real fills often differ slightly from the price you plan for, and fees reduce the actual profit, so treat the potential profit/loss figures as an idealized estimate, not a guarantee.

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