Published · Updated
Expected value (EV) is the average profit per unit wagered if your probability estimate is correct. Positive EV means the model believes the market mispriced the bet. Here's the math + why it's the only metric that matters long-term.
EV = (probability × decimal_odds) - 1
Or expressed as percent: EV % = (prob × decimal - 1) × 100
If a pick has 60% probability at -110 odds (decimal 1.909), EV = (0.60 × 1.909) - 1 = 0.145 = +14.5% per $1 wagered.
Short-term wins and losses are noise. A coin flipper making 20 calls a week hits 60% or better about 25% of the time by pure variance. To know whether you're actually beating the market, you need a metric that smooths variance.
EV is that metric. Over a large sample of +EV bets, your bankroll grows. Over a sample of -EV bets, it shrinks, even if you have winning streaks. Long-term ROI converges to mean EV.
EV and edge are related but distinct.
Edge measures probability disagreement; EV measures expected return per dollar. A pick with 5% edge at -300 odds has different EV than 5% edge at +200, though the edge is identical, the payout structure changes EV.
You need a probability estimate that disagrees with the market in a positive direction. Three ways:
For every priced pick we display, EV is computed from our model probability and the posted price at the time the card is built (vig included), not against a de-vigged or closing line. First-inning reads have no price, so they carry no EV. Picks with positive EV get a recommended stake; picks with negative EV get 0u (Kelly says "don't bet"). The display always shows the EV honestly (even when -10%) so you know which picks the model believes have value vs which don't.
+EV doesn't mean a single bet wins. It means over hundreds or thousands of similar bets, you make money. Picking a +5% EV bet that loses tonight isn't a model failure, it's variance. The same +5% EV bet over 1000 plays expects to return $50 per $1000 staked. That's the math; the variance is just noise.
Theory is one thing, using the concept on tonight's slate is the value. These hubs are the practical application: