Position Size Calculator: How Many Shares to Buy Without Blowing Up Your Account

• Position sizing is the single most important variable in trading — more than entry timing, stock selection, or technical analysis. Getting it wrong ends trading careers.
• The formula is simple: Position Size = (Account Risk ÷ Trade Risk per Share). Risk 1% of capital per trade, and even 20 consecutive losses only costs 20% of your account.
• Most retail traders size positions based on "how much can I afford" — this leads to over-concentration in single trades and account blow-ups.
• Volatility-adjusted position sizing (using ATR) keeps risk consistent across different stocks and market conditions.

Use our free Position Size Calculator to find exactly how many shares to buy for any trade setup, based on your account size, risk tolerance, and stop-loss level.

Position Size Formula

Position Size (shares) = Account Risk Amount ÷ Risk per Share

Where:

• Account Risk Amount = Total Capital × Risk % per trade (typically 1–2%)
• Risk per Share = Entry Price − Stop Loss Price

Example:

• Trading capital: ₹10,00,000
• Risk per trade: 1% → ₹10,000 max loss
• Trade: Buy Infosys at ₹1,500, stop loss at ₹1,450
• Risk per share: ₹1,500 − ₹1,450 = ₹50

Position Size = ₹10,000 ÷ ₹50 = 200 shares Trade value: 200 × ₹1,500 = ₹3,00,000 (30% of capital deployed)

If stop loss hits: lose 200 × ₹50 = ₹10,000 = exactly 1% of capital. Controlled.

The 1% and 2% Rules Explained

1% Rule: Risk no more than 1% of total trading capital per trade. Best for: beginners, volatile markets, low-conviction setups.

2% Rule: Risk no more than 2% of total trading capital per trade. Best for: experienced traders, high-conviction setups, trending markets.

Why these limits matter — consecutive loss simulation:

At 10% risk per trade, just 10 consecutive losses destroys 65% of your account. At 1%, 10 losses costs only 9.6%. Protecting capital through position sizing is what keeps you in the game long enough to be profitable.

Position Size Calculator Table

Capital: ₹5,00,000 | Risk: 1% = ₹5,000 per trade

Notice: position size depends on the stop distance, not the stock price. A ₹2,000 stock with a tight stop can have a larger position than a ₹500 stock with a wide stop.

Volatility-Adjusted Position Sizing (ATR Method)

Standard position sizing uses a fixed stop distance. ATR-based sizing adapts to current market volatility — preventing over-sizing in volatile markets and under-sizing in calm ones.

ATR-Based Position Size:

Stop Loss Distance = N × ATR(14) Position Size = Account Risk ÷ (N × ATR)

Where N = volatility multiplier (typically 1.5–3×)

Example — Nifty 50 index: ATR(14) = 180 points N = 2× multiplier Stop distance = 2 × 180 = 360 points

Account risk: ₹10,000 Position size = ₹10,000 ÷ 360 = 27.7 → round down to 27 units

During high-volatility periods, ATR expands → position size automatically shrinks → less capital at risk when markets are unpredictable.

F&O Position Sizing: Lot-Based Constraints

In futures and options, you cannot buy fractional lots. Position sizing must account for the fixed lot size.

Example — Nifty Futures: Lot size: 50 units Current price: ₹24,500 1 lot value: 50 × ₹24,500 = ₹12,25,000 Margin required (approx. 10%): ₹1,22,500 per lot

Capital: ₹5,00,000. Risk per trade: 1% = ₹5,000 Stop loss: 100 points below entry Risk per lot: 100 × 50 = ₹5,000

Lots to trade: ₹5,000 ÷ ₹5,000 = 1 lot (exactly matches risk budget)

If stop is 50 points: risk per lot = ₹2,500 → could trade 2 lots. If stop is 200 points: risk per lot = ₹10,000 → exceeds budget for 1 lot → skip the trade or reduce risk %.

Portfolio-Level Position Sizing

Individual trade position sizing prevents catastrophic single-trade losses. Portfolio-level rules prevent catastrophic correlated losses.

Portfolio limits:

• Single trade: Max 1–2% capital at risk
• Single stock: Max 10–15% of portfolio value in one name
• Sector: Max 25–30% in one sector
• Correlated assets: Treat correlated positions (e.g., two banking stocks) as one position for risk purposes

Correlated positions example: Long HDFC Bank and Long ICICI Bank simultaneously — both drop when banking sector sentiment turns. Position sizing each at 1% risk underestimates true sector exposure. Treat as a single 2% position.