No vig calculator: the no vig fair odds calculator behind two prices
- The vig, the amount over 100 (%)
- 4.76
- First side, implied probability as priced (%)
- 52.38
- Other side, implied probability as priced (%)
- 52.38
- The two added together (%), over 100 is the overround
- 104.76
Every figure on this site comes out of the prices you type and the arithmetic printed beside them. There is no feed, no price of our own and no third-party data: the site holds no odds at all, only the method for reading the ones you already have. Conversions are exact, not approximations, and the American-to-probability step is written out on each page so you can check it by hand.
The prices above are a worked example (4.76). Type the two you are actually looking at and every line re-computes.
Download the No Vig Calculator and No Vig Odds Calculator worked example (CSV)
Give it the two American prices on a market and it returns what each one implies as a probability, what the two add up to, how much of that total is margin, and the fair price on each side once the margin is taken out. On a standard minus 110 pair the two sides imply 52.38% each, 104.76% together, and the fair price on both sides is even money. Everything is computed in your browser from the numbers you type; nothing is stored and nothing is sent anywhere.
No Vig Calculator and No Vig Odds Calculator: what people ask about the arithmetic
What is the vig, exactly?
It is the amount by which the implied probabilities on a market add up to more than 100%. On the standard two-sided pair it is 4.76 points. It is the charge for the market being made, and it is the reason a raw implied probability always overstates the chance of the outcome.
What is the difference between vig and hold?
Vig is the overround in points above 100. Hold is that same amount expressed as a share of the whole book, so 4.76 points on a total of 104.76 is a hold of 4.55%. Hold is the more useful of the two for comparing markets, because it does not grow simply because a market has more outcomes priced.
How is the margin removed?
By dividing each side's implied probability by the total of both. It assumes the margin sits proportionally on both sides, which is the standard method and the one this calculator shows. It is not the only method in use, and on markets with a strong favourite it tends to understate the favourite slightly.
Does a fair price mean the outcome is 50-50?
No. It means that, with the charge taken out, the market prices that outcome at the probability shown. It is the market's view without the margin on top, and it is a starting point for comparison rather than a statement about what will happen.
Where the method behind this calculator comes from
Levitt, How Do Markets Function? An Empirical Analysis of Gambling on the National Football League (NBER working paper 9422). The paper that measures how a book actually prices a two-sided market rather than balancing it, which is why the two prices you are reading almost never add to 100%.
Wolfers and Zitzewitz, Prediction Markets (Journal of Economic Perspectives, NBER working paper 10504). Sets out the standard reading of a market price as a probability, and the conditions under which that reading holds.