Position Sizing Calculator

Position sizing calculator determines how many shares/contracts to trade based on account size, risk tolerance, and stop loss distance. The fundamental formula: position size = (account × risk %) / (entry - stop). Most professional traders risk 1-2% per trade. 100k account × 1% = 1,000 max risk per trade.

Example: 100k account, 1% risk per trade = 1,000 risk. Stock entry 50, stop 45 = 5 risk per share. Position size = 1,000 / 5 = 200 shares. Position value = 10,000 (10% of account). If stopped out: lose 1,000 (1% of account). If 2x reward target: gain 2,000 (2% of account, 2:1 reward/risk).

Position sizing math: 1% risk per trade allows for 100 consecutive losses before account zero (mathematically impossible odds). 2% risk: 50 consecutive losses. 5% risk: 20 consecutive losses (much more likely with normal probability). Bigger position sizes amplify profits but also drawdowns - professional traders rarely exceed 2% risk per trade. Match position size to your strategy's win rate and reward/risk profile.

A worked example

Try the defaults: account size of 100,000, risk per trade of 1%, entry price of 50, stop loss price of 45. The tool returns 200 shares. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.

What moves the number most

The result responds to Account Size, Risk Per Trade %, Entry Price, and Stop Loss Price. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.

The formula behind this

Position size = (account × risk %) / (entry price - stop loss). Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.

Using this well

What this doesn't capture

Steady-rate math ignores real-world volatility. Actual returns are lumpy; sequence-of-returns risk matters most in drawdown; fees and taxes drag on compound growth; and behaviour changes in drawdowns can reduce outcomes below the projection. The number represents one scenario rather than a forecast.