Bookmaker margin: what it is and what counts as expensive

7 November 2026 · 4 min read

Every price you see has a cut already baked into it. If you never measure that cut, you are comparing things that are not comparable.

One formula

Take the three prices, invert each, and add them up:

If the sum were exactly 1.00, the book would be taking nothing. In practice it always sits above 1.00, and the difference is the margin.

Three real shapes

Match	Prices	Sum	Margin
Example A	2.10 / 3.40 / 3.60	1.0481	4.81%
Example B	2.00 / 3.50 / 4.00	1.0357	3.57%
Example C	1.60 / 4.00 / 5.50	1.0568	5.68%

A margin near 2% is a sharp book. Above 6% you are paying a lot for the privilege of being allowed to bet.

Why the favourite is not always the expensive side

Here is the part that surprises people. The margin is not spread evenly across the three outcomes. In some price ranges the outsider carries far more of it than the favourite does.

If you compare prices by looking at the headline number alone, you can end up backing the side that is carrying almost all of the cut.

What to do with this

Before you compare two books on a match, normalise both to fair prices. Then the comparison means something. A price of 3.00 at one book and 3.05 at another are not the same bet if the margins around them differ.