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No-vig calculator

Enter every price in one market, ideally from a sharp bookmaker or an exchange. You get the margin and the fair odds with it removed, by two methods side by side.

Outcomes

3-way is for markets with a draw, such as football match results.

Decimal odds

Result

Overround
–
Hold
–
Power k
–
OutcomeOfferedimpliedMultiplicativefair oddsPowerfair odds
#1–––
#2–––

The smaller number under each fair price is its fair probability. Overround is how far the implied probabilities go over 100%; hold is the share of stakes the bookmaker keeps on a balanced book.

Two ways to take the margin out

A bookmaker's prices always imply more than 100% in total. Take 2.10 and 1.80 on a two-way market: 1 / 2.10 = 47.62% and 1 / 1.80 = 55.56%, which add up to 103.17%. The extra 3.17% is the margin. To find the fair price you need to decide how to share that margin between the outcomes.

Multiplicative (proportional)

Divide each implied probability by the total, so each outcome loses margin in proportion to its size.

fair p i = (1 / odds i) ÷ Σ (1 / odds)

For 2.10 and 1.80 that gives 46.15% and 53.85%, or fair odds of 2.167 and 1.857.

Power

Raise every implied probability to the same power k, with k chosen so they add up to exactly 100%. Small probabilities shrink relatively more than big ones, so more of the margin comes off the longshot. That matches the favourite–longshot bias: bookmakers tend to load more margin onto outsiders, where punters are less price-sensitive.

fair p i = (1 / odds i) ^ k, with k such that Σ fair p = 1

For the same prices, k ≈ 1.047 and the fair odds are 2.175 and 1.851. The difference looks small, but a value-bet edge is often only 2–4%, so a tenth of a point matters.

Where this is useful

Value betting starts with a fair price. Remove the margin from a sharp market (Pinnacle, Betfair Exchange), then look for a bookmaker paying more than that fair price. ArbVantage's value-bet feed does this for every market it tracks. It uses both methods across several sharp sources and keeps the more conservative fair probability, so a price doesn't look like value just because of the method.

FAQ

No-vig questions

What is the vig?
The vig (vigorish), also called the juice, overround or margin, is the bookmaker's built-in edge. Prices are set so the implied probabilities of all outcomes add up to more than 100%. At 2.10 and 1.80 they add up to 103.17%, so the overround is 3.17%. Removing it gives you an estimate of the fair odds.
Which method should I use, multiplicative or power?
Multiplicative spreads the margin in proportion to each outcome's probability. It's simple and close enough for evenly matched two-way markets. The power method takes relatively more margin off the longshot, which matches how bookmakers tend to price (the favourite–longshot bias), so it's usually better for uneven markets and three-way football. When the two disagree, the safer choice is the lower fair probability for the outcome you want to back. ArbVantage's value-bet engine uses both and keeps the more conservative one.
Why are the overround and the hold different numbers?
They measure the same margin in two ways. The overround is how far the implied probabilities go over 100% (Σ − 1). The hold is the share of all money staked that the bookmaker keeps if it has balanced its book (1 − 1/Σ). At 2.10 and 1.80 the overround is 3.17% and the hold is 3.08%.
Can I use any bookmaker's odds?
You can, but the fair price is only as good as the market you put in. Sharp bookmakers and exchanges such as Pinnacle and Betfair have low margins and move quickly on informed money, so their no-vig prices are the usual benchmark. Soft bookmakers' prices are better compared against that benchmark than used as one.
How do I use fair odds to find a value bet?
Compare the fair odds with the best price on offer elsewhere. If a bookmaker offers 2.25 on an outcome whose fair odds are 2.175, the expected value is 2.25 / 2.175 − 1, about +3.4% per bet. The Kelly calculator turns that edge into a stake.

More free tools

Find value bets automatically

ArbVantage removes the margin from Pinnacle and Betfair prices for every market it tracks and flags the bookmakers paying more than the fair price, with the edge and a Kelly stake on each one. Free for 7 days.

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