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Kelly criterion calculator

Enter your bankroll, the odds and your estimated win chance to see the Kelly stake, with half and quarter Kelly alongside, and when Kelly says not to bet at all.

Bankroll, price and estimate

Odds format
Your fraction
$20.83suggested stake (quarter Kelly)
8.33%full Kelly, share of bankroll
$41.67half Kelly
$20.83quarter Kelly

Kelly grows a bankroll fastest only if your win estimates are accurate. Overestimate your edge and full Kelly bets far too much, which is why many people use a fraction of it. It is a staking formula, not a way to win.

Calculations show hypothetical outcomes from the prices you enter. They do not predict results, and betting always involves risk.

Worked example

Bankroll $1,000, odds +120 (2.20 decimal), win estimate 50%. b = 1.2, so f = (1.2 x 0.5 minus 0.5) / 1.2 = 8.33%. Full Kelly is $83.33, half Kelly $41.67 and quarter Kelly $20.83.

Using it sensibly

  • Recalculate from your current bankroll, not the one you started with.
  • Use a fraction of Kelly unless you are very sure of your estimates.
  • Never bet money that isn't part of a bankroll you can afford to lose; see the bankroll calculator.

Related guides

Common questions

What is the Kelly criterion?

A formula for the share of your bankroll to stake when you believe you have an edge: f = (b x p minus q) / b, where b is the decimal odds minus 1, p your win chance and q = 1 minus p.

Why use half or quarter Kelly?

Because win estimates are never exact. Overestimating your edge makes full Kelly stake far too much and swing hard; a fraction keeps most of the growth with much smaller swings.

What if Kelly is negative?

Then at your estimate the price has no edge and Kelly says don't bet.

Does Kelly guarantee profit?

No. It is a staking rule that assumes your probabilities are right. With wrong estimates it can lose money faster than flat staking.

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