What a bookmaker’s margin actually is

Take any three-way football price and turn each of the three numbers into the chance it implies, by dividing one by the price. A price of 2.00 implies a half. A price of 4.00 implies a quarter. Do that for home, draw and away, and add the three together.

If the book were charging nothing, the total would be exactly one. It never is. It comes to something above one, and the amount above one is the margin. A total of 1.05 is a margin of five per cent, and it means the book has priced the match as though the three outcomes between them were five per cent more likely than certain.

That excess is where the bookmaker’s money comes from. It is charged the moment the slip is accepted, on the winning bets and the losing ones alike, and no result changes it. It is the only cost in betting that is completely predictable in advance.

The board on this site converts the margin into the quantity a reader can use directly: what comes back on a cedi of turnover. Divide one hundred by one plus the margin. A five per cent margin returns 95.24 on a hundred staked, which means the price alone costs 4.76 in every hundred that crosses the counter.

Why the margin is not the same as your losses

It is a floor, not a forecast. The figure describes what happens to somebody staking in line with the book’s own prices, spread across everything. A punter who backs the wrong things loses more than the margin, and most punters lose more than the margin.

This matters because a smaller margin is not a route to being ahead. It is a smaller charge on the same activity. Choosing a book that returns 95 per cent rather than 92 does not turn a losing year into a winning one; it makes a losing year less expensive.