How to calculate expected value (EV) in sports betting

Most bettors talk about wins. Sharp bettors talk about expected value. EV is the only number that tells you whether a bet was a good decision — independent of whether it actually hit. Here's how it works, with the math broken down for people who don't want a statistics lecture.

The formula

Expected value = (probability of winning × amount won per bet) − (probability of losing × amount lost per bet).

That's it. If the result is positive, the bet is +EV — over the long run, you make money making that bet. If it's negative, you lose money in the long run, even if you happen to win this one.

Example 1: a coin flip with bad odds

A friend offers you a coin flip. Heads, you win $10. Tails, you lose $11. Probability of winning is 50%, probability of losing is 50%.

EV = (0.5 × $10) − (0.5 × $11) = $5 − $5.50 = −$0.50 per flip. Lose money every time you take it, even though you'll win half the flips.

Example 2: an NFL spread at −110

Standard sportsbook juice. To win $100, you risk $110. You think the team has a 55% chance to cover.

EV = (0.55 × $100) − (0.45 × $110) = $55 − $49.50 = +$5.50 per $110 bet. Real edge — assuming your 55% read is correct.

Example 3: a +250 underdog

$100 bet pays $250. You think the dog wins 35% of the time.

EV = (0.35 × $250) − (0.65 × $100) = $87.50 − $65 = +$22.50 per $100 bet. Big +EV. The book's implied probability at +250 is about 28.6% — you're saying it's 35%. That gap is the edge.

Implied probability — the shortcut

American odds convert to implied probability with two formulas:

• Negative odds: |odds| / (|odds| + 100). −150 → 150/250 = 60%.
• Positive odds: 100 / (odds + 100). +250 → 100/350 = 28.6%.

If your real probability is higher than the book's implied probability, you have +EV. If it's lower, you don't.

The mistake almost everyone makes

Casual bettors confuse "I won the bet" with "I made a good bet." They're different. A +EV bet can lose. A −EV bet can win. Over a thousand bets, the EV math wins. Over five bets, anything can happen.

Track your bets, log the odds, log your estimated win probability, and look at the running EV — not just W/L. That's how you actually find out if you have an edge or if you've just been lucky.

Where peer bets fit in

Most of the EV conversation assumes you're betting at a sportsbook with juice. But a huge share of bets in 2026 happen between friends — group chats, leagues, gym pacts — and those bets often have no juice at all. Even-money bets with someone who's worse at evaluating the matchup than you? That's the highest-EV environment most bettors will ever see. The catch: nobody tracks them.

That's the gap Settled fills. Signed receipts, per-rival win rate, and the EV proof that the loudest predictor in your group chat actually isn't.