What a positive edge actually means
An edge is the gap between our number and the bookmaker's price. Here is how that gap is worked out, and the three things it does not tell you.
Every price a bookmaker publishes is a probability wearing a costume. Decimal
odds of 2.50 are the claim that something happens about 40% of the time,
because 1 divided by 2.50 is 0.4. Read the whole market that way and you can
see what the book thinks, in numbers rather than in odds.
Do that across all the outcomes of a match and you will notice something: the implied probabilities add up to more than 100%. That surplus is the margin: the bookmaker's fee, folded invisibly into every price on the board.
Where the gap comes from
BAI8 works out its own probability for each outcome, from published sources and a fitted model, without looking at what the book is charging. The edge is what is left when you subtract the book's implied probability from ours.
If we make an outcome 45% likely and the book is charging a price that implies 40%, the gap is five points. That gap is the entire claim being made, and it is worth being precise about what it is not.
What it is not
It is not a prediction that the bet will win. A 45% shot loses more often than it wins. A positive edge says that at this price, over many bets like this one, the maths is on your side, not that this particular Saturday will go your way.
It is not a guarantee that our number is right. It is an estimate built from sources that can be wrong, stale, or missing the thing that actually decides the match. When the estimate is wrong, the edge was never there.
And it is not a stake recommendation. How much to risk is a question about your bankroll and your tolerance for a bad month, not about this number.
A positive edge is an estimate, not a promise.
Why the margin matters
A five-point gap sounds convincing until you notice the book's margin on that market was six points. Then the gap is not evidence of a mispriced outcome; it is evidence that you are looking at the fee.
This is why BAI8 compares the same market across many bookmakers rather than one. A gap that survives the widest available price is a different kind of claim from a gap measured against the tightest.
Checking it yourself
The arithmetic is deliberately simple, and you should do it:
- Take the decimal odds and divide 1 by them. That is the implied probability.
- Do that for every outcome and add them up. Anything over 1.0 is the margin.
- Compare our number to the implied one, and see whether the gap is bigger than the margin you just measured.
If it is not, the edge is noise. We would rather you found that out from us than from a losing month.