Expected Value in One Formula
EV = (your probability × profit if win) − ((1 − your probability) × stake). A +150 bet you judge 45% to win has EV of (0.45 × 150) − (0.55 × 100) = +12.5 per 100 staked. Positive EV compounds; negative EV — which is every random bet after vig — decays your roll at a predictable rate.
Estimating True Probability
Your edge must come from somewhere: statistical models, market timing (beating moves), specialization in niche leagues the books staff thinly, or promo exploitation. 'I watch a lot of games' is not an edge — the line already contains everyone who watches a lot of games.
Closing Line Value: Your Report Card
The closing line is the sharpest estimate of true probability available. If you consistently beat the close — betting +150 on lines that close +120 — you almost certainly hold a real edge, and results will follow the math. Track CLV on every bet; it converges to truth hundreds of bets before your win-loss record does.