What position size does the Kelly Criterion recommend based on my win rate and win/loss ratio?

How this is calculated

• Formula: Kelly fraction equals your win rate minus (1 minus your win rate) divided by your payoff ratio, where the payoff ratio is your average win divided by your average loss.
• Full Kelly sizing is mathematically optimal for long-term account growth but produces steep equity swings. Half Kelly and quarter Kelly trade away some growth rate for meaningfully less volatility, which is why most traders who use Kelly at all use a fraction of it.
• If your average win and average loss come from a small sample of trades, the Kelly fraction is only as reliable as those numbers. Recalculate as your trade history grows.
• This calculator does not cap the output. If the math returns an aggressive number, treat that as a reason to lean toward quarter Kelly or a flat percent-risk model, not a signal to size up.
• Pair this with the Risk of Ruin Calculator to see how a specific risk-per-trade percentage performs across a long series of trades before you commit to a number.