Positive EV (+EV) means the bet has positive long-run expected value. Even a small +EV (say +2%) is highly profitable over volume.
Every bet has a probability of winning and a payout if it wins. Multiply the probability by the profit, subtract the probability of losing times the stake, and you get the expected value — the average dollar outcome of placing this bet repeatedly.
The formula: EV = (P(win) × profit if win) − (P(lose) × stake)
If you bet -110 and you genuinely have a 55% win probability, your EV per $100 wager is positive ~$14.55. Find these spots, place them at scale, manage your bankroll, and the math grinds out long-term profit.
The hard part is correctly estimating your win probability. Be honest. Most bettors over-rate their edge. Track your closing-line value (CLV) — if you consistently bet at better prices than the market closes at, your subjective probability estimates are at least directionally correct.