Position Size Calculator

Position sizing answers a question that matters more than most entry or exit signals: given how much you're willing to lose if a trade goes wrong, how many shares should you actually buy? This calculator uses the fixed-fractional method, a standard risk-management rule where you risk a set percentage of your account on any single trade, and let your stop-loss distance determine the share count.

The result is that every trade, regardless of the stock's price or volatility, risks the same dollar amount relative to your account, which is the foundation most professional risk management is built on.

How does this calculator work?

Enter your account size and how much of it you're willing to risk on this trade, expressed as a percentage (many traders use 1% or less per trade).

Enter your planned entry price and stop-loss price. The distance between them is your risk per share.

The calculator divides your dollar risk budget by the risk per share to get the position size, rounded down to a whole share, so your actual risk never exceeds your budget.

Sizing by a fixed fraction of the account keeps risk constant whether you're buying shares outright, shorting them on margin, or defining risk with an options position. Pairing a consistent risk budget with each trade's probability of profit is the core of position management, and measuring the results by risk-adjusted return shows whether the sizing is actually paying off.

Worked example

A $50,000 account, risking 1% per trade, buying at $100 with a stop-loss at $95.

Dollar risk budget

$500

Risk per share

$5

Position size

100 shares

Position value

$10,000 (20% of account)

How the numbers work

1% of $50,000 is a $500 risk budget for this trade. Since each share risks $5 (the gap between the $100 entry and $95 stop), $500 divided by $5 is exactly 100 shares.

That 100-share position is worth $10,000, or 20% of the account, even though only $500 (1%) is actually at risk if the stop is hit. The position size scales automatically with how tight or wide your stop is: a tighter stop allows a larger position for the same dollar risk, and vice versa.

Position sizing this way keeps risk consistent across trades with very different stop distances or share prices, so a volatile stock with a wide stop doesn't accidentally risk far more of your account than a stable one with a tight stop.