Kelly criterion calculator
How much to bet — sized to your edge.
Edge (EV)
+10%
Stake % of bankroll
4.17%
Recommended stake
41.67
Positive edge — half Kelly suggests staking 41.67 (4.17% of your bankroll).
Kelly sizes the stake to your edge. Most bettors use half or quarter Kelly to smooth variance — and your win-probability estimate has to be honest, or the number is meaningless.
What is the Kelly criterion?
The Kelly criterion is the bet size that maximizes long-run bankroll growth given your edge. It needs two honest inputs: the price, and your estimate of the true win probability. With an edge it stakes more; with none, it stakes nothing.
Full Kelly is aggressive and swingy, so most disciplined bettors use half or quarter Kelly to cut variance while keeping most of the growth. Bankroll Guardian applies the same Kelly and unit sizing to every bet you log — and tracks whether your probability estimates actually hold up over time.
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