Stocks & Investing · Introduction
Kelly Criterion & Trading Expectancy
Estimate EV and full, half or quarter Kelly sizing from win rate and payoff ratio.
Updated 2026-10-25 · ThinkVault Tools
What can this tool help you do?
Estimate EV and full, half or quarter Kelly sizing from win rate and payoff ratio.
Check the purpose and assumptions, then open the tool. Return to the guide for details.
Purpose and inputs
Purpose and inputs
Use win rate and payoff ratio to estimate EV, full/half/quarter Kelly and capital allocation.
Method and assumptions
Let p be win probability and b=average win/average loss. EV=p×win−(1−p)×loss; full Kelly=p−(1−p)/b. Multiply by 1, 0.5 or 0.25 and clamp allocation to 0–100%. This is an educational binary-stake risk proxy, not the exact growth-optimal exposure for stocks with partial losses; correlations, gaps and costs are excluded.
Method
Let p be win probability and b=average win/average loss. EV=p×win−(1−p)×loss; full Kelly=p−(1−p)/b. Multiply by 1, 0.5 or 0.25 and clamp allocation to 0–100%. This is an educational binary-stake risk proxy, not the exact growth-optimal exposure for stocks with partial losses; correlations, gaps and costs are excluded.