Margin / vig calculator — find the true no-vig odds
The margin (also called vig, juice or overround) is the built-in profit a bookmaker adds to a market's odds. It is found by converting every outcome's price to implied probability, summing them, and subtracting 100% — the amount over 100% is the bookmaker's margin. Removing that margin proportionally from each price gives the fair, no-vig odds.
The formula
Implied probability for each outcome = 1 ÷ decimal odds. Overround = sum of all implied probabilities. Margin % = (overround − 1) × 100. Fair (no-vig) probability for outcome i = (1 ÷ oddsᵢ) ÷ overround. Fair odds = 1 ÷ fair probability.
Try it
Enter decimal odds greater than 1.00 for every outcome.
Overround
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Margin
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Fair (no-vig) odds
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Why odds never reflect true 50/50 probability
In a perfectly fair, zero-margin 2-way market, both outcomes would be priced at exactly $2.00 (50% implied probability each), summing to exactly 100%. In practice, a bookmaker prices both sides slightly below their fair value — for example $1.91 and $1.91 — so the implied probabilities sum to more than 100%. That excess is the bookmaker's guaranteed margin, collected regardless of the outcome.
The same principle scales to 3-way markets (home/draw/away) and multi-runner racing markets — more outcomes generally means a larger total overround, because the bookmaker is pricing more uncertainty and collecting margin across more runners.
Worked example: two-way market
Odds of $1.91 / $1.91: implied probability each = 1 ÷ 1.91 = 52.36%. Overround = 52.36% + 52.36% = 104.71%. Margin = 4.71%. To find the fair odds, divide each outcome's implied probability by the overround: 52.36% ÷ 1.0471 = 50.00% fair probability each, giving fair odds of exactly $2.00 on both sides — as expected for a symmetric two-way market.
Using margin to compare bookmakers
A lower margin on the same market means a better price for punters, all else equal — the bookmaker is taking a smaller cut. Comparing the overround across operators on the same race or match is one of the more reliable ways to judge which book is offering genuinely competitive pricing, rather than relying on a single headline price.
Reference table
Worked margin examples
Odds (decimal)
Overround
Margin %
Fair odds
1.91 / 1.91
104.71%
4.71%
2.00 / 2.00
2.10 / 1.80
102.06%
2.06%
2.14 / 1.84
2.50 / 2.90 / 3.40 (3-way)
111.44%
11.44%
2.79 / 3.23 / 3.79
1.50 / 2.75
103.30%
3.30%
1.55 / 2.84
Frequently asked questions
How much vig is a bookmaker taking on evens-money odds?
Two $1.91 prices on a 2-way market carry a 4.71% margin — a common overround for major Australian sportsbook markets. To find it: 1 ÷ 1.91 = 52.36% per side, sum both sides (104.71%), subtract 100%.
What is the difference between vig, juice, margin and overround?
These are different names for the same thing — the bookmaker's built-in profit margin on a market, expressed as the percentage by which implied probabilities exceed 100%. 'Vig' and 'juice' are US terms; 'margin' and 'overround' are used more broadly, including in Australia and the UK.
How do you calculate true (no-vig) odds from a 3-way market?
Convert each of the three prices to implied probability (1 ÷ odds), sum all three to get the overround, then divide each individual implied probability by the overround to get its fair probability. Convert each fair probability back to decimal odds (1 ÷ fair probability).
Does a lower margin mean a bookmaker is more trustworthy?
Not necessarily — margin reflects pricing competitiveness on a specific market, not licensing or trustworthiness. Always separately verify ACMA licensing before depositing with any Australian-facing bookmaker, regardless of how competitive its margins are.