What Is Betting Edge? Expected Value & Vig Explained

Part of our complete guide to +EV betting.

What Is a Betting Edge?

A betting edge is the gap between your own estimate of an outcome's probability and the probability implied by the sportsbook's price. If you think a team wins 60% of the time but the price implies 50%, that 10-percentage-point gap is what people mean by "edge."

It is worth being honest about what this concept does and does not promise. Estimating probabilities more accurately than an efficient market is genuinely hard, and most bettors don't manage it over the long run. Understanding edge is about understanding how betting value is defined — not a guarantee that value is easy to find or capture.

Edge is also different from simply picking winners. You can pick winners 55% of the time and still lose money if you bet heavy favorites. Edge is about whether a price is mispriced relative to the true probability — that is where the idea of value comes from.

How Sportsbooks Set Lines

Sportsbooks aren't trying to predict outcomes perfectly. Their goal is to set lines that attract roughly balanced action on both sides. When the money is balanced, the book profits regardless of the result — it collects its cut (the vig, or juice) from the losing side.

Most standard bets are priced at -110 on each side. That means you risk $110 to win $100. When a book has $110 on each side, the loser pays $110 while the winner receives $100 plus their $110 stake back. The book keeps the $10 difference. That built-in margin is the vig, and it is what makes a real edge harder to find than it looks.

Implied Probability: What the Odds Are Really Saying

Every set of odds can be converted into an implied probability — the win percentage the odds suggest. This is the core concept behind understanding betting value.

For American odds at -110, the implied probability is:

110 / (110 + 100) = 52.38%

So the book is pricing the outcome as if it happens about 52.4% of the time. Here's the catch: both sides of a standard -110 / -110 line imply 52.4%, which adds up to 104.8% — not 100%. That extra 4.8% is the vig, baked into both sides.

A few more examples of implied probability:

-150 odds imply 60.0% (150 / 250)
+150 odds imply 40.0% (100 / 250)
-200 odds imply 66.7% (200 / 300)
+200 odds imply 33.3% (100 / 300)

Converting odds to implied probability is what lets you compare what the market thinks to what you think.

The Breakeven Math: Why 52.4% Matters

At standard -110 odds, you risk $110 to profit $100. If you bet 100 games:

At a 50% win rate: 50 wins (+$5,000) and 50 losses (-$5,500) = -$500
At a 52.4% win rate: 52.4 wins (+$5,240) and 47.6 losses (-$5,236) = roughly breakeven
At a 55% win rate: 55 wins (+$5,500) and 45 losses (-$4,950) = +$550

This is why picking winners slightly more than half the time still loses money. The vig creates a hurdle rate of 52.4% that you have to clear before a single dollar of profit appears. Everything above 52.4% is where returns would come from — which is exactly why the vig matters so much.

Devigging: Turning Odds Into a Fair-Price Estimate

Because the vig is baked into both sides of a line, a single book's odds overstate the true probabilities. Removing it — "devigging" — gives a cleaner estimate of the fair price. The steps:

Convert each side's odds to an implied probability.
Normalize both sides so they add to 100%. This strips the vig back out.
Repeat across several books and average the results for a fair-odds consensus — a benchmark for what the price "should" be.

A common refinement is leave-one-out: to judge one book's price, build the consensus from the other books, so the comparison isn't circular. And because sharp books like Pinnacle post the tightest margins, their prices are often used as the anchor for a fair-price benchmark.

Once you have that benchmark, you can see which book is offering the best available number on a given side. Comparing prices across books and taking the best one is line shopping — the most durable habit in betting, because it improves the price on a bet you were going to make anyway. EdgeBets runs this comparison across books every day so you can see the best available price at a glance: compare today's odds across sportsbooks.

When a Price Difference Actually Matters

Not every gap between a book's price and the consensus means something. Small differences — a point or two of implied probability — are often just noise: books update at different times, prices get rounded, and lines jitter around the consensus minute to minute. A difference only stands out when it is larger than that normal variation.

This is why comparing across several books is more reliable than eyeballing one: a single book being a little off is noise, while a price that sits clearly away from the consensus is easier to trust as a real difference. It is the same reason a fair-odds benchmark is more useful than any one book's number in isolation.

EdgeBets compares prices across sportsbooks so you can see the best available number on each game — compare today's odds — and publishes daily model projections.