Position Size Calculator
Work out the exact number of shares, contracts, or units to trade so a single loss never costs more than you decided to risk. Enter your numbers below — it updates as you type. Free, no signup.
Risk per trade is the % of your account you're willing to lose if the stop is hit. Most disciplined traders keep this at 0.5–2%.
Your position
Sizing right is step one. Knowing whether your setups are actually +EV is step two — that's what a real journal tells you.
Track your trades free — no card required →How position sizing works
Position sizing is the single most important risk decision you make on every trade — more important than the entry itself. The goal is simple: never let one trade lose more than a small, fixed fraction of your account, so that a normal losing streak can't blow you up. The math is the fixed-fractional rule:
For example, on a $50,000 account risking 1% ($500), buying at $100 with a stop at $95, your risk per share is $5. So you buy $500 ÷ $5 = 100 shares, a $10,000 position. Notice that a tighter stop would let you buy more shares for the same $500 of risk — that surprises a lot of traders.
How to use this calculator
- Account size — your total trading capital.
- Risk per trade — the % you'll lose if the stop hits (0.5–2% is typical).
- Entry price — where you plan to get in.
- Stop-loss price — where you'll exit if you're wrong.
The calculator returns your share count, the dollars you're risking, the position's value, and what percent of your account it ties up.
Sizing is step one. Knowing your edge is step two.
Correct sizing keeps you in the game, but it won't tell you which of your setups actually make money. That answer lives in your trade history — win rate by setup, average R-multiple, the leaks that quietly drain your account. That's what TradeFlow Quantum does: connect your broker, your trades import automatically, and it surfaces the patterns you can't see in a spreadsheet.