Most people look at a set of odds and see one thing: how much they collect if they win. It is the natural reading and it is the one the bookmaker wants you to make. But odds say something more useful, and almost nobody reads it.
Odds to probability: one division
Divide 1 by the decimal odds and you have the probability the bookmaker assigns to that result. Odds of 2.00 are 50%. Odds of 4.00, 25%. Odds of 1.50, 66.7%. Nothing else is needed: one division and the odds stop being a prize and become a forecast with a number on it.
This changes how you decide. The question stops being 'how much do I collect?' and becomes 'is this result really as likely as the odds say?'. If you think it is more likely, there may be value. If you think it is less, you are being sold something expensive.
Careful: that probability is inflated
One detail you cannot forget: the probability you pull out of the odds includes the bookmaker margin. That is why, if you add up the three results of a match, it comes to more than 100%. The real probability of each result is somewhat lower than the one the odds imply. The odds never play in your favour — not even when you read them well.
The comfortable-favourite mistake
Reading odds as probabilities protects you from a classic trap: the short price. A 1.20 looks like safe money. It is 83% — and a 17% chance it does not come in. Chain a few of those 'safe' ones together and the losing run arrives sooner than you think. A short price is not safety: it is just a high probability with a small prize attached.
Odds do not tell you how much you will win. They tell you how unlikely it is that you win at all.
Reading the probability behind the number does not hand you a crystal ball. It hands you something more modest and more useful: you stop betting blind. That is the least you can ask of a decision where you put money down.