Asian Handicap Win Probability Tool - Odds Margin Removal, Trends & Value Analysis

What is De-vigging?

Asian Handicap is the most common betting market in football. Bookmakers add a margin (also called 'vig' or 'juice') to the odds, making the total implied probability exceed 100%. This means the bookmaker always maintains an edge over time.

The de-vig calculator uses mathematical formulas to reveal the true probability distribution, helping bettors identify which markets offer genuine value. Lower margins are more favorable for bettors; higher margins should be approached with caution.

Calculation Formulas

Implied Probability = 1 ÷ Decimal Odds
True Probability = Implied Probability ÷ Overround × 100%
Bookmaker Margin = (Overround - 1) × 100%

Reading the bookmaker's margin

Take the reciprocal of each price and add them up. That total is the bookmaker's implied probability. Anything above 1 is the margin. With a home price of 1.90 and an away price of 1.95: 1 ÷ 1.90 = 0.5263 and 1 ÷ 1.95 = 0.5128, which sum to 1.0391, a margin of 3.91%. The lower the margin, the better the price is for you.

Recovering the true probability

Divide each side's implied probability by the total to strip the margin out. In the same example the home side comes to 0.5263 ÷ 1.0391 = 50.65% and the away side to 49.35%, which now sum to exactly 100%. Invert those for the fair odds: 1.974 and 2.026. The gap between the real price and the fair price is what the bet costs you.

The Kelly criterion

Kelly gives the share of your bankroll to stake given a known win probability. The formula is (b × p − q) ÷ b, where b is the decimal odds minus 1, p is the probability of winning and q the probability of losing. A negative result means there is no edge and the bet should not be made. This tool computes it for you and shows negative values as zero.

One limit worth knowing

If you recover probabilities from a bookmaker's own two prices and then measure expected value against those same prices, the answer is always negative and identical on both sides: exactly −margin ÷ (1 + margin). At 1.90 / 1.95 both sides return −3.77% and Kelly is zero on both. That is not the tool failing; it is arithmetic. You cannot use a bookmaker's own prices to prove that those prices are good value. The tool earns its keep when you take the true probability from one source, such as a low-margin book or your own model, and measure a different bookmaker's price against it.

Worked examples

1. Home 1.90 / away 1.95

A margin of 3.91%, true probabilities of 50.65% and 49.35%, and fair odds of 1.974 and 2.026. Expected value is −3.77% on both sides and Kelly is zero on both. This is a high-margin market with no value on either side.

2. Home 2.10 / away 1.85

The margin is only 1.67%, giving true probabilities of 46.84% and 53.16% and fair odds of 2.135 and 1.881. Expected value is still negative at −1.65%, but the cost is far lower. On the same match, a margin falling from 3.91% to 1.67% makes an enormous difference over time.

Frequently asked

What is the Kelly criterion?

It is the stake size, as a share of bankroll, implied by a win probability and a price. The formula is (b × p − q) ÷ b, where b is decimal odds minus 1, p the win probability and q the loss probability. At odds of 2.10 with a 55% chance, b is 1.10 and Kelly is (1.10 × 0.55 − 0.45) ÷ 1.10 = 14.1%. A negative figure means no edge.

Why is the expected value always negative?

Because the probability was derived from the same pair of prices you are measuring. Feed in one bookmaker's two prices and expected value always equals −margin ÷ (1 + margin), identical on both sides. To find a positive figure you need a probability from a different source to measure this bookmaker's price against.

What counts as a reasonable margin?

On a two-outcome market, 2% to 4% is typical and anything under 2% is sharp. The higher the margin, the more accurate you have to be simply to break even. Comparing the margin on the same match across bookmakers is the most direct cost comparison there is.

What are fair odds for?

Fair odds are the prices that correspond to the true probabilities once the margin is removed. If a bookmaker offers more than your fair price, that price favours you; less, and it does not. It is the most direct way to compare prices between bookmakers.

* This explains how the odds calculations work. Figures are based on the values you enter, are provided for reference only, and are not betting advice.