Position Size Calculator

Calculate the optimal number of shares to buy based on your account size, risk tolerance, and stop-loss level. Never risk more than you can afford to lose.

Your total trading capital

Maximum % of account to risk (typically 1-2%)

Below entry for long positions

Shares to Buy

200

Position Value

$30,000.00

% of Portfolio

30.0%

Dollar at Risk

$2,000.00

Risk Per Share

$10.00

Position type: Long

Profit Targets (Risk/Reward Scenarios)

1:1 R/R

+$2,000.00

Target: $160.00

2:1 R/R

+$4,000.00

Target: $170.00

3:1 R/R

+$6,000.00

Target: $180.00

R/R = Risk/Reward ratio. A 2:1 ratio means you aim to make $2 for every $1 risked.

Position Sizing Tips

  • 1The 2% Rule: Never risk more than 2% of your account on a single trade. This protects you from catastrophic losses.
  • 2Volatility Matters: For highly volatile stocks, consider using a smaller risk percentage (0.5-1%).
  • 3Respect Your Stop: Always honor your stop-loss. Moving it further away defeats the purpose of position sizing.
  • 4Account for Slippage: In fast-moving markets, you may exit at a worse price than your stop. Factor this into your risk.

Tools that do this with live data

This calculator works from the numbers you enter. These tools pull company data in automatically.

TradingView

Advanced interactive charting

Free; Essential $12.95/month billed annually

Check pricing at TradingView

Finviz

Fast fundamental and technical stock screener

Free; Elite $39.50/month or $299.50/year

Check pricing at Finviz

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How It Works

  1. 1Enter your total account or portfolio size.
  2. 2Set your risk percentage per trade (typically 1-2% for conservative traders).
  3. 3Enter your planned entry price for the stock.
  4. 4Set your stop-loss price (where you'll exit if the trade goes against you).
  5. 5The calculator shows how many shares to buy to stay within your risk limits.

The formula

  • Maximum risk = Account size × Risk per trade
  • Risk per share = |Entry price − Stop-loss price|
  • Shares = Maximum risk ÷ Risk per share, rounded down

Worked example

Account of $100,000, risk 2% per trade, entry at $150, stop-loss at $140.

  1. 1Maximum risk: $100,000 × 2% = $2,000
  2. 2Risk per share: $150 − $140 = $10
  3. 3Shares: $2,000 ÷ $10 = 200

Buy 200 shares: a $30,000 position (30% of the account) that risks $2,000 if the stop is hit.

Frequently Asked Questions

What is position sizing?

Position sizing is a risk management technique that determines how many shares or contracts to trade based on your account size and the amount you're willing to risk. Proper position sizing helps protect your portfolio from large losses on any single trade.

What percentage should I risk per trade?

Most professional traders risk 1-2% of their account per trade. Conservative traders may risk 0.5-1%, while more aggressive traders might go up to 3%. Never risk more than you're comfortable losing entirely.

Why is the stop-loss important?

The stop-loss determines your risk per share. A tighter stop-loss means less risk per share, allowing you to buy more shares while maintaining the same total dollar risk. However, tighter stops may get triggered more often.

What if my calculated position is larger than I'm comfortable with?

You can always buy fewer shares than the calculator suggests. The calculator shows the maximum position size for your risk parameters. Consider reducing position size for volatile stocks or uncertain market conditions.

Should I use this for every trade?

Yes! Consistent position sizing is one of the most important aspects of successful trading. It ensures that no single trade can significantly damage your portfolio, regardless of whether it wins or loses.