Position Size Calculator
The position size calculator tells you exactly how many shares, units, or contracts to buy so you never risk more than a defined percentage of your trading account on a single trade. Simply enter your account size, your risk tolerance (typically 1–2%), your entry price, and your stop loss price — the calculator does the rest instantly.
Position Size (Units/Shares)
50.00
Dollar Risk
$100.00
Position Value
$2,500.00
Risk per Unit
$2.0000
How to use this calculator
- 1
Enter your account size
Type in the total value of your trading account in dollars. Use your current equity, not margin balance.
- 2
Set your risk percentage
Choose how much of your account you are willing to lose on this trade. Most professional traders use 1% or less.
- 3
Enter your entry price
Input the price at which you plan to enter the trade — your buy price for a long or sell price for a short.
- 4
Enter your stop loss price
Input the price at which you will exit the trade if it goes against you. This defines your maximum loss per unit.
- 5
Read your position size
The calculator instantly shows how many units or shares to buy, your total dollar risk, and the position value.
Formula
Position Size = Dollar Risk ÷ Risk Per Unit
Dollar Risk = Account Size × (Risk % ÷ 100)
Risk Per Unit = |Entry Price − Stop Loss Price|First, calculate your dollar risk: multiply your account size by your risk percentage (e.g., $10,000 × 1% = $100). Then divide that by the distance between your entry and stop loss (the risk per unit). The result is how many units to buy. For example, a $100 risk with a $2 stop distance gives a position size of 50 shares.
Worked Example
Account size: $10,000 Risk percentage: 1% ($100 risk) Entry price: $50.00 Stop loss price: $48.00 Dollar Risk = $10,000 × 1% = $100 Risk Per Unit = $50.00 − $48.00 = $2.00 Position Size = $100 ÷ $2.00 = 50 shares You would buy 50 shares. If the trade hits your stop loss at $48.00, you lose exactly $100 — 1% of your account. Your total position value is 50 × $50 = $2,500.
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