Enter the decimal price on every outcome in the market, not one price on its own. The calculator adds the implied probabilities, removes the bookmaker’s margin proportionally, and returns a margin-free probability and a fair price for each side. The overround it reports is the margin it took out.
What the Margin Does to a Market
Convert each price in a market to a probability and the total lands above 100%. That surplus is the bookmaker’s margin, and it is why the prices on the board are shorter than the chances they represent.
Stripping the vig scales every implied probability down until the set sums to exactly 100%, then converts each one back into odds. What comes out is the market’s own opinion with the charge removed, which is the number worth comparing against a price somewhere else.
The single-price version of this job belongs to the Implied Probability Calculator. Measuring the margin rather than removing it belongs to the Hold / Vig Calculator. This page does the middle step: take the whole market in, hand fair odds back.
A Worked Example
A two-way market priced at 1.65 and 2.20.
- Implied probabilities: 1 ÷ 1.65 = 60.61% and 1 ÷ 2.20 = 45.45%.
- Market total: 106.06%, so the overround is 6.06%.
- No-vig probabilities: 60.61 ÷ 106.06 = 57.14% and 45.45 ÷ 106.06 = 42.86%.
- Fair odds: 1 ÷ 0.5714 = 1.750 and 1 ÷ 0.4286 = 2.333.
A cleaner case makes the mechanic obvious. Take a market at 1.90 on both sides. Each price implies 52.63%, the pair sums to 105.26%, and normalising leaves 50% each. The fair odds come back as 2.00 and 2.00, which is where a coin-toss market sits once nobody is charging for it.
Using Fair Odds as a Benchmark
The 2.333 in the example is the number to carry across to other bookmakers. Anything above it on that outcome pays more than the originating market thinks the chance is worth, and anything below it pays less.
Fair odds also give you a probability you did not have to model. Feeding 42.86% into the Expected Value Calculator against a price of 2.50 elsewhere tests whether the gap is worth backing, and the Kelly Criterion Calculator will size it from the same figure.
Which market you strip matters more than the strip itself. A sharp bookmaker’s closing line stripped of margin is a serious probability estimate. A recreational book’s Tuesday morning price stripped of margin is a recreational book’s opinion with cleaner decimals on it.
Proportional Removal Is an Assumption
The calculator divides every implied probability by the same total, which assumes the bookmaker loaded the same percentage of margin onto each outcome. Odds compilers do not always work that way. Where they shade one side harder than the other, proportional removal returns fair odds that are wrong on both sides, and wrong in a direction you cannot see from the prices alone.
Alternative methods exist for that reason. Some strip the margin in equal probability points rather than in proportion, and some fit a power or Shin adjustment that pushes more of the margin onto longer prices. Run the same 1.65 / 2.20 market through two of them and the fair prices will differ in the third decimal, which is enough to change a marginal bet into a pass.
The larger caution is what fair odds are not. 1.750 and 2.333 describe what this bookmaker thinks after the charge comes off. If the pricing was soft to begin with, the calculator hands you a soft opinion in tidier clothes.
Fair Odds Without a Market to Copy
Gecko Edge builds the probability from the football rather than from someone else’s price: Poisson goal models with a Dixon-Coles correction, blended with market and league priors, producing win probabilities and fair odds across 130+ leagues. That gives you a second opinion to set against the stripped market price, instead of a cleaner copy of the same one.
Further Reading
- All betting calculators: the full library of 34 free tools
- The anatomy of a value bet: how AI spots what the bookies miss
- Why the same line moves from -EV to +EV over time
What does no-vig mean in betting?
No-vig odds are the prices a market would show if the bookmaker charged nothing. Every price in a market converts to a probability, those probabilities sum above 100%, and the surplus is the vig. Removing it scales the set back to 100% and converts the result into odds, giving a margin-free view of the same market.
How do you calculate no-vig odds?
Convert each price with 1 ÷ decimal odds, add them, then divide each one by that total. A market at 1.65 and 2.20 gives 60.61% and 45.45%, summing to 106.06%. Dividing through returns 57.14% and 42.86%, and inverting those gives fair odds of 1.750 and 2.333.
Are no-vig odds the true odds?
They are the bookmaker’s opinion with the charge removed, which is a different thing from the true chance. The calculation also assumes margin sits evenly across outcomes, and compilers sometimes weight it towards one side. Treat fair odds from a sharp book as a strong estimate and fair odds from a soft book as a weak one.
What is the difference between no-vig odds and implied probability?
Implied probability converts one price on its own: 2.20 implies 45.45%, margin included. A no-vig calculation needs every price in the market, because removing the margin means knowing how much the whole book adds up to. The first number tells you what a price says, and the second tells you what the market means.