How it works
Convert every price to implied probability with 1 ÷ oddsand add them up. A market with no margin sums to exactly 100%. Anything above is the bookmaker's cut.
What is a normal number?
- 4–6% — typical for a two-way head-to-head market at a single Australian bookmaker.
- Under 2% — usually only reachable by taking the best price on each side from different books.
- Below 0% — the market sums under 100% and backing every outcome profits regardless of the result. That is arbitrage, and it is rare and short-lived.
One thing this cannot see
If any price comes from a betting exchange, it is quoted before commission on winnings — usually around 5% — so the real margin is worse than it looks here. Take the commission off that price first.