What is the vig, and how do you remove it?
The vig is the bookmaker's margin, baked into every price you see. Until you take it out, you are not looking at what the market thinks will happen — you are looking at what the market thinks, plus a fee. Stripping it out is the first step in deciding whether a price is worth taking.
What is the vig in betting?
Vig is short for vigorish. You will also see it called the overround, the margin, the juice or simply the book percentage — all the same thing: the commission a bookmaker builds into its prices so that it profits on a balanced market regardless of the result.
The way to see it is to convert every outcome in a market into the probability it implies, and add them up. A genuinely fair market would total exactly 1.00 — one whole event, no more and no less. A real one always totals more. That excess is the vig.
How do you calculate the vig from decimal odds?
overround % = (sum of all implied probabilities − 1) × 100
Take an even head-to-head priced 1.90 on both sides. Each implies 1 ÷ 1.90 = 0.5263, and together they sum to 1.0526. Subtract one and the overround is 5.26%. The bookmaker is selling you 105.26% of an event that can only be 100%.
The more outcomes a market has, the more places there are to hide margin. A two-way head-to-head might carry 4–6%; a large field or a long-shot player market can carry considerably more, spread thinly enough that no single price looks unreasonable. That is why comparing headline odds between books tells you less than comparing their margins.
What does de-vigging mean?
De-vigging is removing the margin to recover what the market actually believes. The simplest approach — usually called the multiplicative or proportional method — divides each outcome's implied probability by the total:
For our 1.90 / 1.90 market: 0.5263 ÷ 1.0526 = 0.50 on each side. Once the margin is out, the bookmaker is telling you it is a coin flip — and the fair price for a coin flip is 2.00, not 1.90. The difference between 2.00 and 1.90 is what you are paying to bet there.
The proportional method assumes margin is spread evenly across outcomes, which is a simplification. Bookmakers typically load more of it onto long shots, because that is where casual money goes — so on lopsided markets the proportional method overstates the favourite's fair chance. More involved methods exist to account for that; for most purposes the simple version is enough to tell whether a price is somewhere near fair.
Why does the vig matter more than the odds you see?
Because two bookmakers can advertise the same headline price while charging very different amounts for it. The one carrying less overround across the market is giving you a better deal on every bet you place there, whether or not the specific price you are looking at happens to be the best available.
This is also why de-vigging comes before any judgement about value. A de-vigged probability is the market's honest estimate; comparing it to your own is what turns a price into an expected value calculation rather than a hunch. And once you have bet, whether the market moved past your price is measured by closing line value.
Comparing margins across Australian bookmakers
Margin varies by book, by sport and by market type, and it changes as prices move — so it is arithmetic worth automating rather than doing by hand each time. HaterPicks compares 79 Australian bookmakers on one screen, which is what makes a low-margin market visible next to a high-margin one on the same event.
It is information and tooling, not betting advice. You can also work the numbers yourself with the expected value calculator, or read how HaterPicks works.