Trade sizing methods including fixed fractional, volatility-adjusted, Kelly criterion, and liquidity-constrained sizing

Position Sizing Position sizing is the single most important risk management decision in trading. Your entry signal determines direction; your position size determines survival. A mediocre strategy with proper sizing will outperform a great strategy with reckless sizing over any meaningful time horizon. Core principle : Size determines survival, not entries. Two traders with the same signals but different sizing will have wildly different outcomes. The one who sizes conservatively survives drawdowns and compounds capital; the one who oversizes blows up. Methods Covered Method Best For Key Input Fixed Fractional General trading, most recommended Account risk % Volatility Adjusted Volatile markets, multi asset ATR or realized vol Kelly Criterion Quantified edge with track record Win rate + payoff ratio Liquidity Constrained Low liquidity Solana tokens Pool depth Anti Martingale Trend following strategies Recent P&L streak 1. Fixed Fractional Sizing The most recommended method for most traders. Risk a fixed percentage of your account on each trade. Formula Risk Tiers Tier Risk Per Trade Use Case Conservative 0.5–1% New strategies, drawdown recovery Standard 1–2% Most traders, proven strategies Aggressive 3–5% High conviction setups with strong, measured edge Example With this sizing, if the stop loss is hit, you lose exactly 2% of your account regardless of the token's price or volatility. 2. Volatility Adjusted Sizing Scale position size inversely with volatility. When volatility is high, take smaller positions; when low, take larger positions. This normalizes the dollar risk across different market conditions. Formula Where: target vol : your desired daily portfolio volatility (e.g., 2%) current vol : the token's current daily volatility (from ATR or realized vol) Using ATR This automatically reduces exposure in volatile markets and increases it in calm ones. 3. Kelly Criterion The mathematically optimal fraction of capital to risk, maximizing long term growth rate. Derived from maximizing expected logarithmic utility. Formula Where: p = win rate (probability of winning trade) q = 1 p (probability of losing trade) b = average win / average loss (payoff ratio) f = optimal fraction of capital to risk Equivalent form: f = (p (b + 1) 1) / b Critical Rule: NEVER Use Full Kelly Full Kelly assumes perfect knowledge of your edge. In practice, edge estimates are noisy. Always use fractional Kelly: Fraction Use Case Notes 0.25x Kelly Conservative, recommended default Robust to edge estimation error 0.50x Kelly Moderate, for well measured edges Still significant drawdown risk 1.0x Kelly Never in practice Theoretical maximum, catastrophic if edge is overestimated Example If Kelly is negative, you have no edge. Do not trade. See references/sizing formulas.md for the full mathematical derivation. 4. Liquidity Constrained Sizing Critical for Solana tokens. Even if your risk model says you can take a large position, the pool may not support it without unacceptable slippage. Formula (Constant Product AMM) Rules of Thumb Constraint Guideline Max single trade 2% of pool liquidity Max position 5% of pool liquidity Minimum pool depth 10x your desired position size Example Always check all pools , not just the largest. Aggregate liquidity across Raydium, Orca, and Meteora for the full picture. See the liquidity analysis skill for pool depth assessment. 5. Anti Martingale Sizing Increase size after wins, decrease after losses. This is the opposite of the gambler's fallacy (Martingale). The logic: winning streaks may indicate your strategy is in sync with the market; losing streaks may indicate regime change. Implementation Use conservatively. After 3+ consecutive losses, reducing size by 50% protects capital during drawdowns. Position Sizing Ladder Combine all methods and take the most conservative result: The binding constraint tells you what is limiting your size: Kelly bound : your edge is small, size accordingly Risk bound : standard risk management is the limit Volatility bound : market is too volatile for larger size Liquidity bound : pool cannot absorb more without slippage Account Level Limits Individual position sizing is necessary but not sufficient. You also need portfolio level constraints: Limit Guideline Rationale Max single position 10% of portfolio Diversification floor Max correlated exposure 25% of portfolio Correlated assets move together Max total exposure 50–80% of portfolio Cash reserve for opportunities/margin Max positions 5–10 concurrent Attention and management bandwidth PumpFun / Meme Token Sizing PumpFun and early stage meme tokens require special sizing discipline: Very small positions : 0.1–1 SOL per trade due to extreme risk Scale with bonding curve fill % : smaller when early (high rug risk), slightly larger when proven (graduated to Raydium) Never size based on expected return — size based on acceptable total loss Treat as lottery tickets : expect most to go to zero Position limit : no more than 5–10% of portfolio across all meme positions combined Integration with Other Skills Skill Integration risk management Portfolio level limits, drawdown rules liquidity analysis Pool depth data for liquidity constraints kelly criterion Deeper Kelly math, edge estimation exit strategies Stop loss placement affects fixed fractional sizing volatility modeling Better vol estimates for volatility adjusted sizing slippage modeling Precise slippage estimates for liquidity constraints Files References references/sizing formulas.md — Mathematical derivations for all sizing methods with worked examples references/practical guide.md — Sizing by account size, token type, and common mistakes Scripts scripts/size calculator.py — Calculates position size using all methods, shows binding constraint scripts/portfolio sizer.py — Portfolio risk dashboard with per position risk and available budget Quick Reference

position-sizing