How bookmaker margins work
Every bookmaker builds a margin (also called overround or vig) into their odds. In a perfectly fair market, the implied probabilities of all outcomes would add up to exactly 100%. In reality, they add up to more than 100%, and the difference is the bookmaker's profit margin. A typical SA sportsbook runs a 5-8% margin on football match results and a slightly higher margin on niche markets.
Lower margins mean better value for you. If two bookmakers offer odds on the same match but one has a 4% margin and the other has 8%, the first is giving you prices closer to the true probability. Over hundreds of bets, that difference adds up. This is why comparing odds across licensed operators is worth the small effort.
The calculator above also shows "fair odds" for each outcome. These are what the odds would be if the bookmaker took zero margin. You won't find fair odds at any real bookmaker, but they're useful as a benchmark. If you're getting close to the fair price on your selection, you're getting decent value.
FAQ
What is a good margin for a bookmaker?
For major football markets, anything under 5% is competitive. Betway and Hollywoodbets typically run 4-6% margins on PSL and Premier League match results. Margins on horse racing and niche sports tend to be higher (8-15%).
Does the margin affect my payout?
Yes. A higher margin means lower odds on every outcome, which means smaller payouts. The margin is invisible in the sense that there's no fee line item, but it's built into every price you see.
How do I calculate fair odds?
Take the implied probability of each outcome (1 / decimal odds), add them all up, then divide each individual probability by the total. The result is the true probability. Fair odds are 1 / true probability.
Do margins vary by sport?
Absolutely. High-volume markets like Premier League football carry the lowest margins because bookmakers compete on those prices. Lower-volume markets like SA club rugby or Lucky Numbers carry higher margins because there's less competitive pressure.