Position Size Calculator
Calculate the optimal position size for your trades based on risk management. Never risk more than you should on any single trade.
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Used to calculate margin required
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Understanding Position Sizing
Why Position Sizing Matters
Position sizing is arguably the most important aspect of risk management. It determines how much you can lose on any single trade and directly impacts your ability to survive losing streaks. Professional traders consider position sizing more important than entry timing or even strategy selection.
The goal isn't to maximize profit on individual trades - it's to find the optimal size that maximizes long-term portfolio growth while keeping risk of ruin near zero.
The Position Sizing Formula
The formula ensures your dollar risk stays constant regardless of where you place your stop loss:
Position Size = (Account × Risk %) / |Entry Price - Stop Loss Price|Example: $10,000 account, 1% risk ($100), entry at $40,000, stop at $39,000. Position size = $100 / $1,000 = 0.1 BTC or $4,000 position value.
The key insight: tighter stop losses allow larger positions; wider stop losses require smaller positions. Your risk in dollars remains constant.
Common Risk Percentages Explained
Ultra Conservative: Used by prop firms and institutional traders. Can sustain 100+ losing trades. Recommended for new traders learning.
Conservative: Most popular among professional traders. 10 losing trades = 10% drawdown. Good balance of growth and protection.
Moderate: Often called the "2% rule." 10 losing trades = 20% drawdown. Suitable for experienced traders with proven edge.
Aggressive: High risk. 10 losing trades = 30%+ drawdown. Only for very experienced traders with high win rate systems.
How Top Traders Size Positions
Looking at successful traders on our leaderboard, common patterns emerge:
- Consistent sizing: They don't double down on "sure things" - every trade follows the same rules
- Scaling in: Many split entries into 2-3 portions, allowing better average entry
- Reducing size in drawdown: After 3-5 losses, some reduce to half size until winning again
- Account for volatility: Smaller sizes during high volatility (liquidations, news events)
Common Position Sizing Mistakes
"Betting it all" on high-conviction trades: Even great setups can fail. Oversizing destroys accounts.
Using same position size regardless of stop distance: Wider stops need smaller positions to maintain constant risk.
Increasing size to "make back" losses: Revenge trading with larger size leads to catastrophic losses.
Sizing based on available margin: Just because you have $10k margin doesn't mean you should use it all.
Use our Win Rate Calculator to understand your expectancy, and the Liquidation Calculator to ensure your stop is before liquidation.
Frequently Asked Questions
Optimal position size depends on three factors: your account balance, risk tolerance per trade (typically 1-2%), and the distance from entry to stop loss. Formula: Position Size = (Account × Risk%) / (Entry - Stop Loss). This ensures you never lose more than your defined risk amount on any single trade.
Most professional traders risk 0.5-2% of their account per trade. Conservative traders use 0.5-1%, while more aggressive traders may use 2%. Never risk more than 5% on a single trade - this exposes you to excessive drawdowns and emotional decision-making.
Leverage allows you to control larger positions with less margin, but your risk (in dollars) should remain the same. With higher leverage, you use less margin but your position size (and thus profit/loss exposure) stays calculated by your risk parameters, not by available margin.
Not necessarily. While your risk percentage should be consistent (e.g., always 1%), your position size in dollars/contracts varies based on stop loss distance. Wider stops = smaller position; tighter stops = larger position. This keeps your dollar risk constant.
The 2% rule states you should never risk more than 2% of your trading capital on a single trade. If you have $10,000, your maximum loss on any trade should be $200. This rule helps you survive losing streaks - even 10 consecutive losses only costs 20% of your account.