What is the bookmaker margin?

The margin (overround) is the profit a bookmaker builds into its prices. Add up the probabilities of every outcome of a match: whatever exceeds 100% is the margin.

How is it calculated?

Take odds of 1.90 · 3.50 · 4.20. The probabilities are 52.6% + 28.6% + 23.8% = 105.0%, so the margin is 5%. Over the long run, roughly 95.2 of every 100 units staked are paid back to players (100 ÷ 1.05).

Why does it matter?

The higher the margin, the more “expensive” the odds. In the world market, margins on major leagues are usually low, while lower leagues and some national lotteries can reach 15–20%. For the same match, lower-margin odds sit closer to the true probability.

Margins compound on accumulators

When several matches are combined, each match's margin stacks on the others. With a 5% margin on each, a four-match combination carries a total effect of about 21.6% (1.05⁴ ≈ 1.216). That is why harbigol shows the joint probability and fair odds of Today's Market Four separately.

harbigol does not offer betting. Margin information is provided to help you understand how odds are formed.