Vig & Margin Calculator
Enter every outcome in a market and see what the bookmaker is charging you. The margin is the single most reliable number in betting: it is the only edge that is guaranteed, and it belongs to them.
What the vig actually is
Turn every price in a market into an implied probability and add them up. In a fair market they sum to exactly 100% — one of these things must happen. A bookmaker’s market sums to more, and the excess is the margin, also called the vig, the juice or the overround. It is not a fee you pay separately; it is baked into every price you see, and you pay it whether you win or lose.
What a normal margin looks like in Australia
On a mainstream two-way market — head to head, a big line, a popular player prop — an Australian book typically runs somewhere between 4% and 7%. Under 3% is genuinely sharp and usually means a book that limits winners quickly. Above 8% you are in territory where you need a very strong opinion to make the bet worth taking: the price has to be wrong by more than the margin before you are even level.
Why it matters more than almost anything else
A 5% margin means the market has to be wrong by more than 5% in your favour before you make a cent. That is the bar every bet has to clear, on every bet, forever. It is also why line-shopping is the only edge that requires no opinion at all — the same bet at a book with a 4% margin instead of a 7% one is three percentage points of pure, free improvement.
The formula
total book = Σ pᵢ × 100
margin % = (Σ pᵢ − 1) × 100
where Dᵢ is the decimal price of each outcome in the market.
Worked example
A two-way market priced 1.91 / 1.91 gives implied probabilities of 52.36% and 52.36%. Those add to 104.71%, so the total book is 104.71% and the margin is 4.71%. Price the same market 1.95 / 1.95 and the margin falls to 2.56% — the same bet, three-quarters of the cost.
See the margin on every market at once
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FAQ
What is the vig in betting?
The vig — also called the margin, the juice or the overround — is the bookmaker’s built-in edge. Add up the implied probability of every outcome in a market: a fair market totals 100%, and anything above that is the margin.
What is a good margin?
On mainstream Australian two-way markets, 4–7% is typical, under 3% is sharp, and over 8% is expensive. Exotic markets and same-game multis carry far more.
Do I pay the vig even when I win?
Yes. It is not a separate charge — it is in the price. A winning bet at a shortened price simply pays you less than a fair market would have.
Does a lower margin mean better value?
It means a cheaper market, not a good bet. A 2% margin on a price you have no opinion about is still a losing proposition long term. Low margin plus a genuine edge is what you want.