Vig Calculator: Free No-Vig Fair Odds, Overround and Hold

How to calculate the vig on any market

For what the margin is and why hold and overround are two different numbers, see what vig is in betting. This page is the arithmetic.

Take every outcome in the market, convert each price to its implied probability, and add them together. If the market were fair the total would be exactly 100%. It never is. A two-way market priced at −110 on both sides sums to 104.76%, and that 4.76% excess is the overround: the margin built into the prices.

The hold is the same fact expressed as money. Of every dollar staked across the market, the book expects to keep 4.55 cents. The conversion between the two is fixed: hold equals overround divided by one plus overround. That is why a vig calculator should print both instead of picking one, because the American industry quotes them interchangeably and they are never the same number.

Both matter, and they answer different questions. Overround tells you how far the prices sit from honest. Hold tells you what it costs you to bet into them. When somebody says a book holds 4.5% on spreads they mean the second one; when a pricing model reports 4.76% it means the first.

What no-vig fair odds are for

Once the margin is measured it can be removed. Scale every implied probability down proportionally until the set sums to exactly 100%, then convert each one back to a price. Those are the no-vig fair odds, and they are the most useful output this calculator produces.

They do two things. First, they make sportsbooks comparable. One book at −108 and −112 and another at −105 and −115 are not offering the same market, and comparing the two headline prices will not tell you which. Strip the margin from each and you can see what each one actually thinks, and which one is charging more for the view.

Second, they turn a price into a probability you can argue with. A fair price of +100 says the market makes this a coin flip. If you think it is closer to 55%, the disagreement is now explicit and quantified, rather than buried under a margin that made every price look slightly worse than the market's own opinion.

Proportional normalisation is the standard method and it is the one used here, but it is worth knowing it is not the only one. It assumes the margin is spread evenly across outcomes in proportion to their probability. Real books often load more of it onto longshots, so a fair price derived this way tends to be slightly generous to the favourite and slightly harsh on the outsider. For two-way markets close to even the difference is negligible. On a wide three-way market it is not, and it is why this page reports the method, not just the answer.

Two-way, three-way and what changes

A two-way market is a spread, a total, or a moneyline in a sport without draws. Standard American pricing puts both sides near −110 and the hold lands near 4.55%. That is the floor for most of what a typical bettor touches.

Three-way markets add the draw, which is soccer's full-time result and hockey's regulation result. Add an outcome and the book has another price to load, so margins widen: 6% to 8% is ordinary where a two-way market would be under 5%. The arithmetic does not change at all. Add the third probability to the sum and the same formulas run.

Player props and exotic markets are where the numbers get uncomfortable. A two-way prop priced at −125 on both sides carries an 11.1% hold, more than double a standard spread, and it is quoted in exactly the same visual style. Nothing on the screen announces the difference. Running the prices through a vig calculator before betting is the only way to see it, and it takes about ten seconds.

There is a practical habit in that. Before betting an unfamiliar market, price the whole market rather than the side you want, and compare the hold with the 4.55% a standard spread carries. If it is double, the bet needs to be roughly twice as good to be worth the same amount, and that comparison is available before any money moves.

The same check explains why margins differ so much between markets that look alike on a screen. Books hold less where volume is high and pricing is competitive, and more where it is neither. Main lines on major sports are the tightest markets an ordinary account can reach; the further a market sits from that, the more of the price is margin, and the less the headline number tells you on its own.