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How to Remove the Vig: Calculating No-Vig Fair Odds

Learn how to strip the bookmaker's margin from a two-way market and find the fair price, with formulas and a worked example you can follow.

By DataOdds Team

2 min read

In short: Convert each side's odds to an implied probability, add them up, then divide each probability by that total. The results are the no-vig probabilities, and converting them back to odds gives the fair price.

Every price a sportsbook offers has a margin built in. Removing that margin, the vig, gives you the market's fair price: the odds the book would offer if it charged nothing. Fair prices are the starting point for finding value, comparing books and judging whether a bet is worth making.

Convert odds to implied probability

American odds convert to an implied probability with one of two formulas.

OddsFormulaExample
Negative-odds / (-odds + 100)-150 → 60.00%
Positive100 / (odds + 100)+130 → 43.48%

Decimal odds are simpler still: the implied probability is 1 / decimal odds.

Measure the overround

Add the implied probabilities of every outcome. In a fair market they would sum to exactly 100%. Anything above that is the book's margin, called the overround.

For a market priced at -150 / +130:

  • 60.00% + 43.48% = 103.48%
  • The overround is 3.48%

The classic -110 / -110 market sums to 104.76%, which is why it is often described as a "4.76% vig" market.

Normalize to remove the vig

The simplest way to remove the margin is the multiplicative method: divide each side's implied probability by the total.

  • Favourite: 60.00% / 103.48% = 57.98%
  • Underdog: 43.48% / 103.48% = 42.02%

The two now add up to 100%. Converted back to American odds, that is roughly -138 / +138.

Fair odds are the price at which a bet breaks even over the long run. If you can get better than -138 on the favourite somewhere else, you are being paid more than the market thinks the outcome is worth.

When the simple method falls short

The multiplicative method spreads the margin evenly across both sides. In practice, books often load more of the margin onto longshots, so other methods exist:

  • Additive: subtract an equal share of the overround from each side.
  • Power: raise each probability to a common exponent so they sum to 100%.
  • Shin: models the margin as protection against informed bettors.

For near-even markets the methods agree closely. They diverge most in lopsided markets and in futures with many outcomes.

Putting fair odds to work

Once you have a fair price, compare it with what other books are offering. A price better than fair is a positive expected value bet; a price worse than fair is a bet you are paying the margin on. Doing this by hand across dozens of books is slow, which is what an odds screen is for.

Frequently asked questions

What is the vig in sports betting?
The vig (or juice) is the margin a sportsbook builds into its prices. It is the amount by which the implied probabilities of every outcome in a market add up to more than 100%.
What are the no-vig odds of -110 / -110?
Each side implies 52.38%, for a total of 104.76%. Dividing each side by the total gives 50% and 50%, so the no-vig fair price is +100 on both sides.
Is the no-vig price the true probability?
No. It is the market's estimate with the margin removed. How close it sits to the true probability depends on how sharp the book is and how much money has shaped the line.

For educational purposes only. Bet responsibly and only where legal.

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