Expected Value & Kelly Criterion Calculator
Calculate expected value, betting edge and optimal Kelly criterion stake size. Determine if a bet has positive EV and how much to wager.
Expected value (EV) is the single most important concept in profitable betting. A +EV bet means you expect to profit over many repetitions; a -EV bet means the house wins long-term regardless of short-term luck. This calculator takes your bookmaker odds and your estimated true probability of an outcome, then computes the EV, your edge over the book, and the Kelly criterion optimal stake. The Kelly formula tells you exactly what fraction of your bankroll to risk to maximize long-term growth without going bust. Most professional bettors use half-Kelly or quarter-Kelly to reduce variance while still capitalizing on their edge. For APAC markets where line shopping between Pinnacle, SBOBET, and Dafabet often reveals 2-5% edges on Asian handicaps, knowing your precise Kelly stake turns a vague feeling of value into a disciplined staking plan.
Enter your odds and the true (fair) probability to calculate expected value and optimal Kelly stake.
How It Works
Enter the decimal odds offered by your sportsbook, your estimated fair probability (as a percentage), and your total bankroll. The calculator shows expected value per unit, your edge, the full Kelly fraction, the recommended Kelly stake in dollars, and the conservative half-Kelly stake.
Frequently Asked Questions
What is a good expected value for a sports bet?
Any positive EV is theoretically profitable long-term. Professional bettors typically target +2% to +5% EV per bet. At Pinnacle's tight margins, finding +3% EV is a strong signal. At higher-margin books like Dafabet or 1xBet, +5% opportunities appear more frequently but come with lower limits.
Why use half-Kelly instead of full Kelly?
Full Kelly maximizes long-term bankroll growth mathematically, but assumes your probability estimates are perfectly accurate — they never are. Half-Kelly achieves 75% of the growth rate with dramatically less variance and drawdown risk. Most sharp bettors use half or quarter Kelly.
How do I estimate the true probability of an outcome?
The best approach is to use Pinnacle's closing line as a baseline — it is the most efficient odds market in the world. Remove Pinnacle's margin (typically 2-3%) to get fair probabilities. If your sportsbook offers better odds than Pinnacle's fair price, you likely have +EV.
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