Position Size Calculator
Calculate the optimal number of shares to buy while keeping your risk within a fixed percentage of your trading account.
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Result
Position Size
20 shares
Risk Amount
$100.00
Price Difference
$5.00
Potential Loss
$100.00
Formula: Position Size = (Account Balance × Risk%) / (Entry − Stop Loss)
Calculation: (10000 × 1% / 100) / (150 − 145) = 20
How to use the position size calculator?
Enter your trading account balance, the percentage of your account you are willing to risk on a single trade, the entry price of the stock or asset, and the stop loss price. The calculator determines the maximum number of shares you can buy while keeping your risk within the specified percentage.
Formula
Example
You have a $10,000 account and are willing to risk 1% per trade ($100). You plan to enter at $150 with a stop loss at $145 — a $5 risk per share. Dividing the $100 risk budget by $5 gives you a position size of 20 shares. If the stock hits your stop loss, you lose exactly $100 (1% of your account).
FAQs
- What if the result is 0 shares? Your stop loss is too wide for the account size and risk percentage. Either reduce the stop loss distance or increase your risk tolerance.
- Why round down to whole shares? For stocks, you cannot buy fractional shares with most brokers. The calculator rounds down to the nearest whole share to stay within your risk limit.
- Can I use this for options or forex? Yes — the formula applies to any trade with a defined entry and stop loss. For forex and options, use the respective contract sizing units instead of whole shares.
Common Use Cases
- Equity swing or day traders sizing positions within a fixed risk budget.
- Account managers calculating maximum position sizes across multiple correlated trades.
- Beginning traders learning to enforce a consistent 1–2% risk rule.