Sat, 04 Jul 2026

How we measure bookmaker margins

Every price a bookmaker publishes carries a built-in cost. Here's how OddsBash measures it from real published odds, and how the SA betting sites compare.

Every bookmaker builds a cost into the prices it publishes. We call it the margin, and it’s measurable straight from the odds a betting site already shows you. No inside information required.

What a margin actually is

Convert every price in a market to implied probability (1 ÷ price) and add them together. A home/draw/away market has three prices; add the three implied probabilities. A fair market with no house edge would sum to exactly 100%. In practice every betting site’s total sits above 100%, and the amount above 100% is the margin, also called the overround. It’s the built-in cost of betting that market, no matter which outcome you back. See how betting odds work for a fuller walkthrough of implied probability.

Why we only count complete markets

A margin only means something once every outcome in a market has a price. Leave one outcome unpriced and the sum understates the true cost, so we exclude any market a betting site hasn’t fully priced from the calculation entirely. We’d rather measure fewer markets accurately than more markets on a distorted basis. Betting sites that price very few complete markets don’t get ranked on that thin a sample; see the current cut-off on our methodology page.

We also average over a rolling window rather than a single snapshot. A betting site’s margin can drift market to market and hour to hour, so one match tells you almost nothing. The average across many matches over time is the number worth trusting.

What a margin costs you

Say one betting site’s market sums to 104%, another’s to 109%. Neither number tells you who wins. What it tells you is how much of your stake goes to the house over time if you bet that market repeatedly. Staked at random across enough bets, a market averaging 4% margin costs you roughly R4 for every R100 wagered, purely from the pricing; a market averaging 9% costs roughly R9. That gap compounds across a season of betting even if your picks are identical.

Margin isn’t the only thing that matters when you choose where to bet. Deposit and withdrawal speed, FICA turnaround and market coverage all count too. It’s simply the one number nobody publishes and almost nobody asks about, so we measure it.

Reading the best-value ranking

Our best-value page ranks licensed South African betting sites by measured average margin, lowest first. Lower means the pricing costs you less over time. It doesn’t mean that betting site has the best price on any single match you’re looking at right now, or the fastest payouts, or the best app. Check the live odds grid for the match in front of you; use the ranking as a longer-run signal, not a substitute for comparing today’s price.

The full calculation, the completeness rule and the current window are all on the methodology page and don’t change without that page changing too.