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Strategy

Kelly Criterion Calculator

Optimal stake size from your edge and bankroll. Full, half, or quarter Kelly.

New to this? Start with:+EV Calculator

Quick start

  1. Enter the line odds the sportsbook is offering
  2. Enter your true win probability estimate
  3. Set your bankroll and pick a Kelly fraction

Try a quick Kelly example

-110 line, 55% true win rate, $1000 bankroll. See the Kelly stake.

odds format selector

Need help with odds formats? Learn this step

Converted

Decimal
Fractional
Probability

Your honest estimate — not the implied probability from the odds.

$
Range$0 – $10,000
Kelly Fraction

Maximum geometric growth. High variance.

Enter odds, true win probability, and bankroll to see the Kelly stake.

Copy a link that opens this calculator with your current values.

How to Use the Kelly Calculator

Enter the Line Odds the sportsbook is offering in any format. Enter your True Win Probability — your honest estimate, not the implied probability from the line. Enter your Bankroll in dollars. Pick a Kelly Fraction: Full for maximum growth, Half or Quarter to soften variance.

Worked example: a -110 line (implied 52.38%), your true estimate is 55%, bankroll $1000, full Kelly. The recommended stake is about $55 — roughly 5.5% of bankroll.

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How it works

Kelly sizes your bet to maximize long-run geometric bankroll growth. The formula needs three inputs: the offered decimal odds, your honest estimate of the true win probability, and your bankroll.

  1. Enter the line — Sportsbook odds in any format — they convert automatically.
  2. Estimate true win probability — Be honest. Inflated estimates lead to oversized bets and ruin.
  3. Pick a fraction — Most disciplined bettors use half or quarter Kelly to soften variance.

Related tools and guides

Use the +EV calculator to validate your edge first, the Pro Toolkit to chain no-vig → EV → Kelly in one flow, and the bankroll guide to put the unit size into context.

Strategy

+EV Calculator

Find bets with positive expected value

Advanced

Pro Betting Toolkit

All-in-one no-vig, EV, and Kelly pipeline

Advanced

Bankroll Management Guide

Learn how to protect and grow your betting budget

Kelly Criterion FAQs

A staking formula that returns the bet size which maximizes long-run geometric growth of a bankroll. Formula: f* = (b·p − q) / b, where b is decimal odds minus 1, p is your true win probability, and q = 1 − p.

Full Kelly is optimal only when your probability estimate is perfect. Half Kelly gives nearly the same long-run growth with about half the variance — most disciplined bettors use it.

A negative f* means no edge — the implied break-even rate exceeds your true win probability. The calculator clamps recommended stake to $0.

EV tells you whether a bet is profitable. Kelly tells you how much to stake on it. Both numbers matter for proper sizing.