Margin

Margin in betting refers to the bookmaker's built-in profit, which is the difference between the true probability of an event and the odds offered to bettors. It ensures the bookmaker makes money regardless of the outcome.

For example, in a 50/50 event, fair odds should be 2.00 (evens) on both sides. However, a bookmaker might offer 1.91 on each side, meaning they keep a small percentage as profit, known as the margin or vig (vigorish). The margin is calculated as the total implied probabilities of all outcomes minus 100%. A lower margin means better value for bettors, while higher margins make it harder to find profitable bets.