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Kelly criterion calculator

Kelly calculates the bankroll fraction to stake when you have an edge over the odds. It only works with a reliable probability estimate . Guessing produces a precise-looking stake based on an unreliable assumption.

Kelly fraction
Edge 9,20% per dollar staked, provided your probability estimate is accurate.
Stake
$20.91
Bankroll fraction
2,09%
after applying the fraction
Full Kelly
8,36%
for comparison

Pure maths. No sign-in needed. Amounts are in USD, just like the platform.

Let the scanner find your next opportunity

Kelly needs an accurate probability estimate. Arbitrage uses price gaps between sportsbooks. BLAKbets detects over 143 arbs daily.

View plans

No trial period. See plans and prices on the homepage. Adults aged 18+ only.

Formula

How the Kelly formula works

  1. 01

    Calculate the edge

    Edge = probability × odds − 1. A 52% probability at 2.10 gives 0.52 × 2.10 − 1 = 9.2%.
  2. 02

    Divide by net winnings

    Full Kelly = edge / (odds − 1). No positive edge means a zero stake.
  3. 03

    Apply a fraction

    Stake = bankroll × full Kelly × fraction (1, ½ or ¼). A smaller fraction reduces volatility.

Example

Example: $1,000 bankroll, odds 2.10, probability 52%

Questions

Frequently asked questions

Does the Kelly criterion guarantee profit?

No. Kelly sizes a bet assuming your probability estimate is correct. Overestimate it and you stake too much. With no genuine edge, Kelly recommends no bet.

Why use fractional Kelly?

Full Kelly assumes an accurate probability and can produce large bankroll swings. Half or quarter Kelly reduces stakes and sensitivity to estimation errors.

Do I need Kelly for arbitrage?

No. Arbitrage stakes are calculated from the prices rather than a probability estimate. Use the arbitrage calculator.

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