What is Positive Expected Value in Sports Betting? How to Calculate EV

A practical explanation of expected value with simple calculations and examples.

EV concept illustration

Most bettors have heard the term "expected value," but do they really know what it means? And even fewer have figured out how to apply it to their bets.

What exactly is Expected Value?

Expected value is the predicted value of a variable — the weighted average outcome. You sum all possible outcomes and weight each by its probability. EV is widely useful in probability problems, investing, and of course sports betting.

In sports betting, EV measures the difference between your expectation for an outcome and the sportsbook’s expectation. When the difference is in your favor, the bet has positive expected value — it is mathematically profitable. The higher the margin, the better.

Positive EV Betting

Positive EV betting means betting only when there’s a positive probability gap between your model (or a sharp reference) and the sportsbook’s price.

Example of positive EV opportunity using FairOdds Terminal
Example: finding a soft price versus a sharper reference.

Why EV matters to bettors

Coin flip EV example

A coin-flip illustrates EV clearly. If a book prices both sides at -110 on a 50/50 event, the implied probability per side is 52.38% due to vig. If you bet €100 on heads 100 times at -110, you’d expect to lose money in the long run — a negative EV bet.

But if the coin is weighted — say 60% heads, 40% tails — the same -110 pricing becomes profitable: over many trials you’d expect to win. That is a positive EV bet.

How to calculate expected value

The formula: EV = (win probability × profit if win) − (loss probability × stake).

If EV is positive, repeating this bet over many trials nets profit on average. Using the 50/50 coin at -110: (0.50 × €90) − (0.50 × €100) = −€5 (−5%). With a 60/40 weighted coin: (0.60 × €90) − (0.40 × €100) = +€14 (+14%).

Vig and fair odds

Books charge vig on every market, so it’s important to remove vig when estimating true probabilities. At -110 on both sides, the combined implied probability is 104.76% — the excess 4.76% is the juice. Removing vig yields fair odds near +100, i.e., 50% per side.

Ready to apply EV? Launch fairoddsterminal.com and start scanning for positive-EV opportunities.