Bookmaker Margin Calculator

How it is calculated

Each decimal price implies a probability of 1 ÷ odds. The tool adds these for the outcomes you enter: sum = 1/home + 1/draw + 1/away. Leave the draw empty for a two-way market and only home and away are summed. The margin (overround) is (sum − 1) × 100 in percent. The payout ratio is 100 ÷ sum, which is the share of stakes returned if bets were spread across all outcomes. Every odds value must be above 1.00; otherwise there is no result. The tool gives these two figures only. It does not show margin-free odds. It does not check that the outcomes cover the whole market, so a missing outcome gives a misleadingly low or even negative margin.

Common mistakes

• Leaving out the draw on a football 1X2 market. With only 2.10 and 3.60 the tool reports a margin of −24.60%, because the missing outcome removes about a quarter of the probability.
• Adding the draw to a market that has only two outcomes, such as tennis. A made-up third price distorts the margin.
• Entering odds from different bookmakers and reading the result as one bookmaker's margin. The figure only describes the set of prices you typed in.
• Typing fractional or American odds. Only decimal odds work, and values of 1.00 or below return no result.
• Reading the margin as the bookmaker's profit. It is the built-in edge on a balanced book, and the actual profit depends on how the stakes are spread.