Crypto Position Sizing with Kelly Criterion – Free Calculator

Why Most Traders Size Positions Wrong

The number one cause of blown trading accounts isn't bad entries — it's bad position sizing. Traders either bet too small (leaving returns on the table) or too large (one losing streak wipes them out). Most traders pick a round number — "I'll risk 2%" — without any mathematical basis.

The Kelly Criterion gives you a mathematically optimal answer: exactly what percentage of your capital to risk on each trade based on your historical win rate and average win/loss ratio.

The Kelly Criterion Formula

f* = W - (1 - W) / R

f* = Kelly fraction (% of capital to risk)
W = Win rate (e.g. 0.55 for 55%)
R = Win/Loss ratio (average win ÷ average loss)

For example: if your win rate is 55% and your average win is 1.5× your average loss:

f* = 0.55 - (1 - 0.55) / 1.5 = 0.55 - 0.30 = 0.25 (25%)

The full Kelly says risk 25% per trade — which is extremely aggressive. Most professional traders use half-Kelly (12.5%) or quarter-Kelly (6.25%) for practical risk management.

🧮 Try the Kelly Criterion Calculator

Enter your win rate and risk/reward ratio to get your optimal position size instantly.

Open Kelly Criterion Calculator →

Step-by-Step: Sizing a Real Crypto Trade

Let's walk through a real example using BTC with a $10,000 account.

Step 1: Know your edge

Before you can size a position, you need to know your strategy's historical performance:

Win rate: 52% (52 out of 100 trades were profitable)
Average win: +$200
Average loss: -$100
Win/Loss ratio (R): 200 / 100 = 2.0

Step 2: Calculate Kelly fraction

f* = 0.52 - (1 - 0.52) / 2.0 = 0.52 - 0.24 = 0.28 (28%)
Half-Kelly = 14%

Step 3: Calculate dollar risk

With a $10,000 account and half-Kelly of 14%:

Risk per trade = $10,000 × 14% = $1,400

Step 4: Size the position with stop loss

If BTC is at $60,000 and your stop loss is at $58,000 (a $2,000 stop per BTC):

Position size = Risk / Stop distance = $1,400 / $2,000 = 0.7 BTC

Use the Position Size Calculator to do this calculation instantly without manual math.

Kelly Criterion Limitations for Crypto

Kelly assumes stationary win rates — crypto markets are highly volatile, so Kelly outputs should be treated as upper bounds, not exact targets. Best practices:

Use half-Kelly or quarter-Kelly — reduces ruin risk while preserving most of the growth advantage
Cap at 5-10% max per trade — regardless of what Kelly says, high-volatility assets warrant extra caution
Recalculate regularly — as your win rate changes with market conditions, so does the optimal Kelly fraction
Never use full Kelly in live trading — it maximizes long-term growth but also maximizes drawdowns