How to
What a bookmaker margin costs you
A payments ledger has one thing to say about odds. The margin is a charge: it is taken out of every price before a bet exists, it applies whether the bet wins or loses, and unlike every other charge on this site it is never shown at the cashier.
What a margin is
Turn every price in a market into an implied probability and add them up. On a fair book the total is one. On a real one it is more, and the excess is the margin. It is the bookmaker's cut, it is expressed as a percentage of the market rather than of your stake, and over many bets it is the dominant cost of betting for anybody who is not consistently beating the prices.
On the figures in this fact base the tightest football book recorded here is BetFox at 4.21% and the widest is Betway at 8.98%. Both figures come with a condition attached and the next section is that condition.
Why the two figures above are not straightforwardly comparable
Read the basis before the number
The margins in this fact base were taken on different samples. Some are medians across every football market on an operator's own feed; one is a mean of ten top-flight fixtures; one rests on two matches from a third-party aggregator because the operator's own site served no prices at all. A top-flight-only figure always flatters, because the top flight is where every book prices most sharply. The basis of each is printed beside it on the sportsbook page.
Against the charges that are disclosed
one bookmaker on this ledger publishes a charge for paying you: betPawa, 1% withdrawal fee charged by betPawa; deposits free. It applies once, to money already won. A margin applies to every stake, every time. For anybody turning a balance over more than a handful of times, the undisclosed charge is the larger one by a wide distance, and it is the one nobody shops for.
That asymmetry is the reason this publication exists in the shape it does. The costs a bookmaker discloses are easy to compare and small. The costs it does not disclose are large and are only visible if somebody collects them.
Questions about margins
Is a lower margin always better?
Better priced, yes. Whether it is the better bookmaker depends on everything else, which is why the margin does not carry points in the index on this site. A sharply priced book that is slow to pay is not a bargain.
Why can I not compare two margin figures directly?
Because the sample behind them differs and the difference is not small. A median across all football on an operator's own feed and a mean of ten top-flight fixtures answer different questions, and the top flight is the sharpest thing any book prices. The basis of every figure is stated on the sportsbook page.
Does the margin change by competition?
Substantially, and in the same direction everywhere: the big European leagues are priced tightest and lower-tier and friendly fixtures are priced widest. Two records in this fact base carry explicit warnings that quoting their top-flight figure unqualified would misrepresent the book by a factor of three.