Position Sizer
Determine exact shares to buy based on your stop-loss and risk tolerance.
Try the calculator
Run the numbers yourself with the inputs below.
Overview
The Position Sizer determines how many shares to buy so that a stop-loss exit costs only a defined percentage of your total portfolio. It is a core risk-management tool for traders who size positions by risk rather than by capital.
How it works
Shares = (Portfolio × Risk %) / (Entry Price − Stop Loss Price)The numerator is your maximum acceptable loss in currency units. The denominator is the loss per share if your stop is triggered. Dividing one by the other gives the largest position that respects your risk budget.
Worked example
Your portfolio is 50,000, you accept 1% risk per trade, your entry is 100, and your stop is 95.
= Capital at risk is 500. Loss per share is 5. You can buy 100 shares for a total position size of 10,000, which is 20% of the portfolio.
When to use it
- Translate a fixed risk budget into a concrete share count
- Compare position sizes across setups with different stop distances
- Avoid oversized positions in volatile names with wide stops
Frequently asked questions
What risk percentage should I use?
Many discretionary traders cap individual trade risk between 0.5% and 2% of total portfolio value. The right number depends on your win rate, average reward-to-risk, and how many positions you hold at once.
What if my stop loss is very close to my entry?
A tight stop produces a large share count for the same risk budget, so the total position size can become a large percentage of your portfolio. Watch the position-size bar to keep concentration in check.
Does the tool consider slippage?
No. Real exits can fill below your stop in fast markets. To stay within your intended risk, set the stop a little wider than your worst-case slippage estimate or reduce the risk percentage.