No-Vig & Fair Odds

Every line a sportsbook posts is padded with a hidden margin called the vig. Strip it out and you're left with the line's true probability — the number you need before you can spot a +EV bet.

What the vig actually is

Why is a 50/50 coin-flip market priced at −110 on both sides instead of an even +100? Because the sportsbook charges a commission. That commission — the vig (short for vigorish), also called the juice — is how books make money no matter who wins.

At −110/−110, the book is implying each side has about a 52.4% chance. But two outcomes can't both be 52.4% likely — that adds up to 104.8%. That extra 4.8% is the vig. It's a phantom probability the book sells to itself, and it's the reason naive bettors slowly bleed out even on 50/50 guesses.

Step 1 — Convert odds to implied probability

American odds convert to an implied probability like this:

Take a real market — say a tennis match priced at −130 for the favorite and +110 for the underdog:

Side	Odds	Implied probability
Favorite	−130	130 / 230 = 56.5%
Underdog	+110	100 / 210 = 47.6%
Total	—	104.1%

The two sides sum to 104.1%. That 4.1% overage is the vig on this market.

Step 2 — Divide out the vig

To get the fair, no-vig probability for each side, divide each implied probability by the total:

Now they sum to a clean 100%. The favorite's true probability isn't 56.5% — that included the book's cut. It's 54.3%. That's your fair number.

Step 3 — Convert fair probability back to odds

Flip the probability back into American odds to get the fair price:

Our underdog's fair probability of 45.7% converts to roughly +119. So the genuinely fair price on that dog is +119 — not the +110 the book posted. If another sportsbook is offering +130 on the same underdog, you've found a +EV bet: you're getting paid +130 for something worth +119.

Why this works best with Pinnacle

Removing the vig only gives you a true probability if the line you started with was sharp. Garbage in, garbage out. That's why serious bettors devig Pinnacle specifically:

• They take the biggest bets in the world. Limits in the six figures mean sharp money pounds any mispricing until it's gone.
• They don't limit winners. Most US books ban or throttle anyone who wins. Pinnacle welcomes them — so their prices are sharpened by the smartest bettors alive.
• Low margin. Pinnacle runs thin vig to begin with, so there's less distortion to remove and the fair number is more reliable.

Devig Pinnacle, and you have the market's best estimate of the truth. Compare it against the softer US books — DraftKings, FanDuel, BetMGM, Caesars — and the gaps between them are your edges.

The catch: doing it live, everywhere, all at once

The math on one market takes thirty seconds. The problem is that there are thousands of markets across a dozen books, the lines move every few seconds, and a +EV gap can vanish before you've finished typing it into a calculator. Devigging by hand is fine for learning the concept and impossible as a strategy.

That's exactly the job Iron Marker automates: pull Pinnacle's line, remove the vig, compare it to every US book in real time, and surface only the bets where the price beats fair value — with the Kelly stake already calculated.

Frequently asked questions

What is the vig in sports betting?

The vig (short for vigorish, also called the juice or the margin) is the bookmaker's built-in commission. It's the reason a coin-flip market is priced at −110 on both sides instead of +100: at −110 you risk $110 to win $100, and that extra $10 of risk is the book's cut. You can see the vig directly by converting both sides of a market to implied probabilities and adding them up — a fair market would sum to exactly 100%, but a real one sums higher, and the overage is the vig. Removing it is the only way to recover the line's true implied probability, the number every expected-value calculation depends on.

How do you calculate no-vig odds?

Convert both sides of the market to implied probabilities, add them together, then divide each side by that total. Worked example: a market priced at −130 / +110 implies 56.5% and 47.6%, which sum to 104.1% — so the vig is 4.1%. Divide through and the favorite's fair probability is 56.5 / 104.1 = 54.3%, the underdog's is 47.6 / 104.1 = 45.7%, and the two now sum to a clean 100%. Convert those fair probabilities back to American odds and you have the no-vig price for each side. This is the multiplicative method — the standard default — though other methods exist for lopsided markets.

Why use Pinnacle's no-vig line?

Devigging only recovers a true probability if the line you start from is sharp — garbage in, garbage out. Pinnacle is the standard reference because it accepts the largest bets in the world and, crucially, does not ban or limit winning bettors. That policy means the sharpest players keep hammering any mispricing until it disappears, so Pinnacle's line is continuously corrected by the smartest money in the market. It also runs a thinner margin than typical US books, so there's less vig distorting the number in the first place. Devig Pinnacle and you get the market's best estimate of the truth; devig a slow recreational book and you've merely cleaned up a wrong number.

What is the difference between implied probability and no-vig probability?

Implied probability is the straight conversion of the posted odds — at −110 it's 110 / 210, about 52.4%. But posted odds include the book's margin, so the implied probabilities across a market always sum to more than 100%, and each individual number overstates the outcome's real chance. No-vig probability is what remains after you strip that margin out and rescale the sides so they sum to exactly 100% — at −110 / −110, each side's no-vig probability is exactly 50%. The distinction matters because raw implied probability makes every bet look worse than it is: you'd be treating the book's commission as if it were real probability. All EV math should run on no-vig numbers.

Can you remove the vig from three-way or player prop markets?

Yes — the same logic extends to any market where every outcome has a price. For a three-way soccer market (home / draw / away), convert all three sides to implied probabilities, sum them, and divide each by the total, exactly as with two sides. Player props are trickier in practice: some books post only one side, the vig is usually heavier than on main lines, and thin markets make the devigged number a noisier estimate of truth. When both sides are posted, devig them as a pair; when only one side exists, you can't extract a fair number from that book alone and need a sharp two-sided price on the same prop as your reference.

Iron Marker is an analytics tool, not a sportsbook, and this guide is educational — not betting or financial advice. Odds shown are illustrative. Must be 21+. Problem gambling? Call 1-800-GAMBLER.