CALCULATOR

Bookmaker Margin Calculator

Enter decimal prices for every mutually exclusive outcome in one market. The sum above 100% is the overround, a simple way to describe the excess implied probability in the listed prices.

A Kenyan football supporter checking generic odds on a phone while watching a match — Illustration for this learning tool; it does not represent live odds or a recommendation.

Enter values

Use decimal odds unless a field says otherwise. Values are processed locally in this browser and are not saved.

Enter values and select Calculate. The result is an arithmetic illustration only.

Calculators do not predict match outcomes or estimate the chance of winning a particular bet. Check the relevant market rules and use figures only as an educational illustration.

Formula

Raw implied probability for each outcome = 100 ÷ odds. Overround = sum of raw probabilities − 100%.

Example

If a three-way market sums to 105%, its overround is 5 percentage points. This is not a direct measurement of the bookmaker’s realized profit.

What this result tells you

The sum of the prices’ raw implied probabilities and the overround above 100%.
A normalized split that rescales the raw figures to total 100%, for comparison only.

What it leaves out

It does not reveal the exact margin on every outcome, operational costs or actual long-term profit.
The calculation assumes the entered prices cover every mutually exclusive outcome.

Common errors

Omitting a draw in a 1X2 market.
Mixing prices from different events or bookmakers.
Calling overround the guaranteed payout reduction on one bet.