Kelly Criterion Calculator for Traders
The Kelly formula gives the bet size that grows an account fastest in theory. In practice traders use a fraction of it.
Kelly criterion
The mathematically optimal risk per trade. Use a quarter to half of it.
%
R
- Full Kelly
- 25.0%
- Half Kelly
- 12.5%
- Quarter Kelly
- 6.3%
How it works
- Kelly % = win rate − (loss rate ÷ reward-to-risk). Half-Kelly halves it for safety.
Questions
- Should I risk the full Kelly amount?
- Usually not: full Kelly produces large drawdowns and assumes your win rate is known exactly. Quarter to half Kelly is common.
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