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Position Size Calculator

How many shares should this trade be? Set what you are willing to lose and where the trade is wrong — the size follows from those two numbers, not from a hunch.

That is $100 on this trade.

Direction

4% from entry

Your position size

50shares

Trading whole shares, that is 50 shares, risking $100 — at or just under your $100 budget.

Maximum Risk

$100

Risk Per Share

$2

Position Value

$2,500

25% of account

Long
  1. 01Maximum Risk
    $10,000 × 1%$100
  2. 02Risk Per Share
    $50 − $48$2
  3. 03Position Size
    $100 ÷ $250 shares
  4. 04Position Value
    50 × $50$2,500

How position size is calculated

Position size is not a preference — it is arithmetic. Two decisions you have already made determine it completely: how much money you are willing to lose on this trade, and how far your stop sits from your entry.

The first gives you a dollar budget. The second tells you what one share of that risk costs. Divide the budget by the cost and you have your size.

Position Size

Maximum Risk ÷ Risk Per Share

$10,000 × 1% = $100 maximum risk

$50.00 − $48.00 = $2.00 risk per share

$100 ÷ $2.00 = 50 shares

Notice what happens when the stop moves. A tighter stop means a smaller risk per share, which means more shares — but the same $100 at risk. A wider stop means fewer shares, and still the same $100. The dollar risk is fixed by you; the size adapts to the trade.

Because most equities trade in whole shares, round down rather than up. Rounding down keeps your actual risk at or just under the budget you set. Rounding up quietly breaks the rule the whole calculation exists to enforce.

The concepts behind it

Position SizeThe amount of an asset you buy or sell in a single trade.Risk Per TradeThe fixed share of your account you are willing to lose on any single trade.Stop DistanceThe gap between your entry and your stop loss — your risk on a single unit.Stop LossA predefined exit that closes a losing trade before the loss becomes serious.Notional ValueThe total market value of a position — size multiplied by price.

This website provides educational information only. It is not financial, investment, or trading advice. This calculator assumes your stop fills at the stop price. Gaps and slippage can push the real loss beyond it.