Position Sizing Calculator: How Much to Trade Per Stock

Position sizing is the most important and most overlooked aspect of trading. Two traders with identical strategies will have dramatically different results based on how they size their positions. This guide and calculator will transform your risk management.

Why Position Sizing Matters More Than Your Strategy

A 60% win-rate strategy can still blow up your account with poor position sizing. Conversely, a 45% win-rate strategy can be profitable with excellent position sizing. Position sizing determines the magnitude of your gains AND losses. It’s the mathematical foundation that turns an edge into consistent profits.

The Fixed Percentage Method

Formula: Position Size = (Account Size × Risk Percentage) ÷ (Entry Price – Stop Loss Price). Example: ₹5,00,000 account, 1% risk = ₹5,000 risk. Buying stock at ₹500 with stop at ₹485 (₹15 risk per share). Position = ₹5,000 ÷ ₹15 = 333 shares. This automatically adjusts position size to your risk tolerance.

The Kelly Criterion for Advanced Traders

The Kelly Criterion calculates optimal position size based on your win rate and risk-reward ratio. Formula: Kelly % = (Win Rate × Average Win / Average Loss – Loss Rate) / (Average Win / Average Loss). Example: 55% win rate, 2:1 R:R → Kelly = (0.55 × 2 – 0.45) / 2 = 32.5%. Most traders use half-Kelly (16%) for safety.

Scaling In and Scaling Out

Instead of entering full position at once: enter 50% at your initial signal, add 25% when trade confirms (moves in your favor), add final 25% at pullback to entry. For exits: take 50% profit at first target, trail the rest. This reduces risk on initial entry while maximizing gains on winning trades.

Position Sizing for Different Account Sizes

₹1,00,000 account at 1% risk: ₹1,000 max risk per trade. ₹5,00,000 account: ₹5,000 max risk. ₹10,00,000 account: ₹10,000 max risk. Regardless of account size, the principle is the same — never let one trade destroy a significant portion of your capital.

Correlation and Portfolio-Level Position Sizing

If you’re long 3 banking stocks, you effectively have one large banking position. Cap your total correlated exposure at 3% risk. If each trade risks 1%, you can have 3 banking trades open simultaneously. This prevents a sector crash from devastating your account.

Frequently Asked Questions

What percentage should I risk per trade?

1-2% for most traders. Beginners should start at 0.5% until they prove consistency. Never exceed 3% regardless of conviction.