What is a Value Bet?
A value bet occurs when the probability of an outcome is greater than what the bookmaker's odds imply. If you estimate a team has a 55% chance of winning and the odds imply only 45%, you have a +10% edge — a value bet.
Expected Value Formula
EV = (Win Probability × Profit) − (Loss Probability × Stake)
For decimal odds of 2.20 with a 55% win estimate: EV = (0.55 × 1.20) − (0.45 × 1) = 0.66 − 0.45 = +0.21 per unit
Why EV Matters More Than ROI
Short-term results are dominated by luck. Over hundreds of bets, positive EV reliably converts to positive ROI. Focusing on edge (EV) rather than outcomes is the foundation of professional betting.
FAQ
How do I estimate my win probability?
Probability estimation is the hardest part of value betting. Approaches include: building statistical models, comparing line movements across bookmakers, using a sharp bookmaker's opening line as a baseline, or applying domain expertise. No method is perfect — track your estimates vs actual results over time to calibrate your model.
What is a good expected value?
Any positive EV is theoretically good. Practically, value bettors look for edges of 3%+ per bet to overcome variance and account for model uncertainty. An EV of 5-10% per bet is excellent and quite rare to find consistently.
Should I use Kelly Criterion with value bets?
Yes — combine this calculator with our Kelly Criterion calculator. Once you know your edge %, Kelly tells you the optimal fraction of your bankroll to stake. Most value bettors use half-Kelly (50% of the full Kelly stake) to reduce variance.