Every price a bookmaker offers carries a hidden percentage. That percentage is the implied probability — the chance of an outcome as suggested by the odds. Learning to read it turns a string of numbers into something you can actually judge.
For decimal odds the conversion is one short sum: divide 100 by the odds. A price of 2.00 implies a 50% chance (100 ÷ 2.00). A price of 4.00 implies 25%, and 1.50 implies roughly 67%. The shorter the price, the higher the implied probability the market is assigning.
Here is the catch. Add up the implied probabilities for every outcome in a market and the total comes to more than 100%. In a two-way market you might find 55% and 52%, summing to 107%. That extra slice above 100% is the bookmaker’s built-in margin, sometimes called the overround or the vig. It is how the book aims to profit regardless of the result.
Knowing this matters because it tells you the true break-even point of a bet. If you believe an outcome is more likely than the implied probability suggests, the price may offer value. If your own estimate is lower, the bet is probably one to leave alone.
18+ · Gamble responsibly · /responsible-gambling/