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Position Sizing Math for Crypto: The Calculator That Survives a 50% Drop

#crypto #position #sizing #bitcoin

Position Sizing Math for Crypto: The Calculator That Survives a 50% Drop

QUICK ANSWER: Position sizing is arithmetic, not willpower. The rule that survives a 50% Bitcoin drawdown: never let one position's worst-case move end the account. Formula — risk per trade = capital × risk%, position size = risk$ ÷ (entry − stop). If BTC can fall 50%, your stop distance and leverage must be set so that 50% adverse move is a bad month, not a blank screen. Most blown accounts used size for the good case, not the worst case.

WHY THIS MATTERS

Discipline fails under fear; math does not. A trader can promise "I'll cut at 2%," but when price gaps, only pre-committed size saves them. Sizing is the only risk control that works while you sleep. In crypto, where 30-50% moves are normal (OBSERVED: 2021-2022 ~77% peak-to-trough), size is survival.

RESEARCH QUESTION / HYPOTHESIS

Hypothesis: Accounts using fixed-fraction sizing (risk% per trade, pre-committed) show lower worst-case drawdown than accounts sized by conviction ("this one is big").

DATA & METHODOLOGY BOX

  • Source: Sizing mechanics, derived from capital/risk math (DERIVED).
  • Period: General; stress-tested on OBSERVED BTC drawdowns (2018 ~84%, 2021-2022 ~77%).
  • Sample: Hypothetical 1 BTC-equiv portfolio, 1% vs 5% risk.
  • Method: Worst-case simulation under 50% adverse gap.
  • Validation: Math is deterministic, not empirical.
  • Baseline: Full-allocation (100% in one position).

RESULTS

Risk% per trade 50% adverse move impact Account status
1% risk, 10% stop distance -10% on that position Alive
5% risk, 50% no-stop gap -50% on that position Hurt, not dead
100% conviction size -50% to -100% Dead

Findings:

  1. Fixed-fraction sizing bounds loss by construction (DERIVED).
  2. Leverage multiplies both directions — 10x turns 5% stop into 50% account.
  3. The 50% crash is the STRESS test, not the edge case, in BTC.
  4. Conviction-sized positions fail exactly when right matters most.
  5. Math pre-committed beats discipline promised.

REPRODUCIBILITY 

capital = 100000
risk_pct = 0.01
entry, stop = 30000, 27000   # 10% stop
risk_dollars = capital * risk_pct
position = risk_dollars / (entry - stop)
print("Position size:", position, "BTC-equiv")
# If BTC gaps -50% from entry with no stop, loss = position * 50% * entry
Enter fullscreen mode Exit fullscreen mode

WHAT FAILED / COUNTER-EVIDENCE

Small size misses big moves — but missing profit is survivable, missing survival is not. The trade-off favours small.

LIMITATIONS

  • Math is DERIVED, not a market prediction.
  • Gap risk (no-stop) exceeds stop distance; size for the gap, not the stop.

PRACTICAL TAKEAWAYS

  1. Risk 1% per trade, max 3% total exposure.
  2. Size for the 50% gap, not the 2% stop.
  3. Leverage capped so worst gap is survivable.
  4. Recompute size after every 20% capital change.
  5. No conviction override — the formula is the rule.

FAQ

Q: 1% too small?
Small is the point. 100 trades of 1% survives; 1 trade of 50% might not.

Q: Leverage with sizing?
Allowed only if 10x gap-loss < total risk budget. Usually means tiny leverage.

Q: Stops get wicked?
Size for gap, not stop. Assume no stop exists.

TL;DR

Sizing is math, not nerve. Risk 1%, size for the 50% gap, cap leverage. The formula survives the crash your discipline won't.

SOURCES

  • BTC drawdowns: public aggregates (OBSERVED).
  • Sizing mechanics: DERIVED from capital/risk arithmetic.

AUTHOR / CANONICAL ATTRIBUTION

Shakti Tiwari — Nifty Option Trader, XGBoost Expert. Educational only, not financial advice.

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