What does no-vig mean?

It means the bookmaker margin has been removed from a price so it reflects the implied probability alone. If two sides are both offered at 1.90 the market adds up to 105.2%, and removing that 5.2% proportionally gives a no-vig price of 2.00 on each side.

How is the fair price calculated?

From the sharp reference book you follow, by removing its margin across the market rather than from the soft book where you place the bet.

Is a bet above fair odds guaranteed to win?

No. Fair odds describe the chance, not the outcome. Beating fair repeatedly is what makes money over hundreds of bets, and any single bet can still lose.

What fair odds mean

The fair price is the number to beat. Here is where it comes from and why it matters more than the size of the drop.

Every price a bookmaker offers has their margin built into it. Strip the margin out and you are left with what the book actually thinks the chance is, expressed as odds. That is the fair price, and in the Terminal it sits in the Fair column beside every drop.

The OddsHub Terminal detail panel showing the fair price beside the max bet — Fair sits beside the max bet in the detail panel, under the price it was calculated from

Taking the margin out of a two-way market

Price offered on each side1.90

Implied chance of each1 divided by 1.9052.6%

The two added togethermore than certainty, so 5.2% is margin105.2%

Share of the book each side is52.6 divided by 105.250.0%

Fair price2.00

Why a price is not the same as a probability

Take a two-way market where both sides are offered at 1.90. If those were honest prices they would imply a 52.6% chance each, which adds up to 105.2%. Probabilities cannot sum to more than 100%, and that extra 5.2% is the margin: the book's cut for making the market.

Removing it proportionally puts both sides at 2.00, or a 50% chance each. That is the de-vigged, or no-vig, price. It is what the book believes, rather than what the book charges.

How to use it

This is why the size of a drop matters less than where the drop finished. A price that fell 9% but is now below fair has already been corrected, and you are late. A price that fell 3% and is still above fair has not been corrected, and you are not.

Two drops, only one of them a bet

Arsenal v SpursOver 2.52m
2.1 to 2.02fair 1.96limit 2.4kBeats fair
Roma v LazioUnder 2.54m
2.2 to 1.88fair 1.94limit 1.9kThrough fair

The second row fell four times as far. It is also the one with nothing left: at 1.88 you are already below the 1.94 fair price and paying the margin. The first row moved barely at all and is still worth taking.

When to be careful with it

Fair is only as good as the price it came from. In a thin market, hours before kickoff, with a small limit attached, the reference price is itself uncertain and so is the fair number derived from it. That is why the limit beside a drop is worth as much attention as the percentage: a large limit means the book is confident enough to take real money at that price.