рџ“ђ What is the Kelly Criterion?
In Simple Terms
The Kelly Criterion is a mathematical formula that helps you determine the optimal position size to maximize your capital growth over the long term.
It was developed by John Larry Kelly Jr. in 1956 at Bell Labs and was originally used for information theory problems.
Why Does It Matter?
- Maximize Growth — mathematically proven to optimize long-term capital growth rate
- Risk Control — prevents betting too much, which could lead to ruin
- Remove Emotions — you always know exactly how much to bet, no guessing
- Discipline — fixed approach to every trade entry
рџ“Љ Kelly Variants Comparison
Full Kelly maximizes growth but increases volatility. Fractional Kelly reduces risk.
| Type |
% of Full Kelly |
Example ($10K, 32.5% Kelly) |
Growth Rate |
Max Drawdown |
| Full Kelly |
100% |
$3,250 |
Maximum |
~50%+ |
| вњ… Half Kelly |
50% |
$1,625 |
75% of max |
~25% |
| Quarter Kelly |
25% |
$812 |
56% of max |
~12% |
| Eighth Kelly |
12.5% |
$406 |
41% of max |
~6% |
рџ’Ў Recommendation for Crypto
Use Quarter Kelly (25%) or Half Kelly (50%). Cryptocurrencies are 3-5x more volatile than FOREX, so full Kelly is too risky. Fractional Kelly reduces portfolio volatility while maintaining significant growth.
рџ“ќ Calculation Examples
Example 1: Typical BTC Trade
1Win Rate: 55%, Risk:Reward: 1:2
2Full Kelly = (0.55 Г— 2 - 0.45) / 2 = 32.5%
3Quarter Kelly = 32.5% Г— 0.25 = 8.125%
4With $10,000 deposit: position = $812.50
5Stop-loss: -$406.25 | Take-profit: +$812.50
Example 2: High Win Rate Setup
1Win Rate: 60%, Risk:Reward: 1:3
2Full Kelly = (0.60 Г— 3 - 0.40) / 3 = 46.7%
3Quarter Kelly = 46.7% Г— 0.25 = 11.7%
4With $10,000 deposit: position = $1,167
Example 3: Unprofitable Setup (Don't Trade!)
1Win Rate: 40%, Risk:Reward: 1:2
2Full Kelly = (0.40 Г— 2 - 0.60) / 2 = 10%
3When win rate below 33% with R:R 1:2 — Kelly is negative, do not enter!
рџ§ Why Does Kelly Work?
Mathematical Foundation
Kelly Criterion maximizes the geometric growth rate — the rate at which your capital grows. This is different from maximizing expected profit.
Imagine you're making 100 trades. Kelly chooses the position size that results in maximum capital after those 100 trades.
Coin Flip Analogy
Imagine a coin that lands heads 60% of the time. You bet on heads.
- If you bet everything — one loss wipes you out
- If you bet 1% — you'll grow, but very slowly
- If you bet 20% (Kelly optimal) — maximum growth
- If you bet 40% — growth is slower than at 20%
Kelly finds the "sweet spot" between betting too little and too much.
Key Insight
Betting MORE than Kelly is WORSE than betting less!
This is counterintuitive, but mathematically proven: staking above Kelly reduces long-term growth. That's why fractional Kelly (25-50%) is the safe choice.
вљ пёЏ Important Warnings
🔴 Kelly Requires Accurate Data
The formula assumes you know exactly your win rate and Risk:Reward. If these estimates are wrong, Kelly will give wrong results. In practice, use Quarter Kelly to compensate for estimation errors.
🔴 Kelly Doesn't Account for Correlation
If you open multiple positions simultaneously (BTC + ETH), they may be correlated. Kelly is calculated for a single trade.
🔴 Kelly Doesn't Guarantee Profit
Kelly maximizes growth with constant win rate and R:R. If these parameters change, results will vary.
вњ… How to Minimize Risks
1. Use Quarter Kelly (25%)
2. Keep a trading journal for accurate win rate
3. Don't open more than 3-5 positions simultaneously
4. Recalculate Kelly every 50-100 trades
вќ“ Frequently Asked Questions
What win rate do I need to be profitable?
With Risk:Reward 1:2 (standard for crypto), you need a win rate above 33.3%. With R:R 1:3, above 25%. The higher your win rate and R:R, the better Kelly works.
How do I calculate my win rate?
Keep a trading journal. Count your winning trades and divide by total trades. You need at least 50-100 trades for statistically significant results.
Can I use Kelly with leverage?
Yes, but carefully. Kelly can give values above 100% (using leverage). For crypto, recommend no more than 3x leverage even with Kelly.
Who uses the Kelly Criterion?
Famous investors: Warren Buffett, Bill Gross, Edward Thorp (formula creator). Also used by hedge funds and professional traders.
How often should I recalculate Kelly?
Recalculate every 50-100 trades or when you notice changes in your win rate. In crypto, due to high volatility, recalculate more often.