How Bookmaker Margins Work
A bookmaker margin is the built-in cut a bookie takes on every market — the reason the odds on a match never add up to a fair 100%. Add up the implied probabilities of all outcomes on a betslip and you get a number above 100%. That extra percentage is the margin (also called the overround or vig). On our sample of 236 markets, Betway ran an average margin of about 6.5%, 10bet came in near 4.8% on 27 markets, and Sportingbet sat higher at roughly 8.6% on 39 markets. Same fixture, different prices — and over a season that gap is real money out of your pocket.
What the margin actually is
When a bookie prices a market, they convert each outcome into odds. In decimal format, the implied probability of an outcome is simply 1 divided by the odds. A fair coin toss priced at true 50/50 would be 2.00 and 2.00, and the two probabilities add to exactly 100%.
No bookie prices it that way. They shade the odds down so the total climbs above 100%. That surplus is the margin. It's how the operator makes money whichever way the result goes, and it's why you can't just back both sides of a two-way market and profit.
The margin is separate from any specific promo, boost or free bet. It's baked into the base price of the market before anything else. That's why comparing raw prices across South African bookmakers matters more than chasing a once-off sign-up offer.
How to calculate the overround yourself
The method is the same for any market on any SA bookie. Convert each price to a percentage, add them up, subtract 100.
- Step 1: For each outcome, work out 1 ÷ decimal odds × 100.
- Step 2: Add all the outcome percentages together.
- Step 3: Subtract 100. What's left is the margin.
Take a Premiership (PSL) match priced as a three-way (home / draw / away). Say the odds are 2.10 home, 3.30 draw, 3.60 away.
- Home: 1 ÷ 2.10 = 47.62%
- Draw: 1 ÷ 3.30 = 30.30%
- Away: 1 ÷ 3.60 = 27.78%
- Total = 105.70%
The overround here is 5.70%. That's the bookie's theoretical hold on the market. A three-way football market carries more outcomes than a two-way market, so it usually shows a slightly bigger overround than, say, an ATP tennis match-winner priced only two ways.
Implied Probability Calculator
A worked example: what margin costs you
Margin isn't abstract — it directly lowers the price you get. Here's the same PSL match compared at two different margins.
Imagine the 'true' fair odds on the home win are 2.00 (a genuine 50% chance). Two bookies price it:
- Low-margin bookie (around 5%): shades the home win to about 1.94.
- Higher-margin bookie (around 9%): shades it to about 1.85.
Stake R500 on the home win and it lands:
- At 1.94 you collect R970 (R470 profit).
- At 1.85 you collect R925 (R425 profit).
Same result, same stake — R45 difference on one bet purely from margin. Scale that across a season of weekend PSL, Premier League and Champions League slips and the compounding matters. This is exactly why our odds sampling tracks best-price share: Betway landed the best price on roughly 91% of the 236 markets we sampled, while Sportingbet topped the price on about 28% of its 39 markets. The bookie with the tighter margin gives you the better number more often.
Why margins differ between markets and sports
Not every market carries the same overround, even at the same bookie.
- Two-way markets (tennis match winner, over/under totals) usually run tighter than three-way football markets, because there are fewer outcomes to load.
- Headline markets on big fixtures — Premier League match result, a UFC main event, a Test match result — tend to be sharper because they attract the most turnover and comparison shopping.
- Niche markets and long lists of outcomes — first goalscorer, correct score, exotic horse racing bets — carry much fatter margins. A correct-score market can hide a double-digit overround because bettors rarely add up 30-plus prices.
- Live betting markets often widen the margin to cover the risk of pricing in-running.
The practical takeaway: the more outcomes a market has, the more room the bookie has to bury margin in it. Stick to headline two- and three-way markets if you want to keep the hold you're paying as low as possible.
Comparing margins across South African bookmakers
Every operator on our list is licensed by a provincial authority — Betway, Sportingbet, Sunbet, LulaBet and 10bet under the Western Cape GRB; Hollywoodbets under the KZN Gaming & Betting Board; Supabets, World Sports Betting and BetXchange under the Gauteng Gambling Board; Easybets under the Mpumalanga Economic Regulator. Licensing keeps them accountable, but it does not standardise their margins. Pricing is a commercial decision, and it varies.
From our sampled odds data:
- 10bet: ~4.8% average margin (27 markets sampled), best price on ~85% of them.
- Betway: ~6.5% average margin (236 markets sampled), best price on ~91%.
- Sportingbet: ~8.6% average margin (39 markets sampled), best price on ~28%.
Sample sizes differ, so treat 10bet's and Sportingbet's figures as narrower snapshots than Betway's broader set. As editorial judgment: Betway's combination of a mid-single-digit margin across a large sample and a very high best-price share is why it prices well on the day-to-day schedule. The lesson for you is simpler than the numbers — keep two or three accounts open and compare the actual price on the specific game before you stake.
How to beat the margin in practice
You can't remove the margin, but you can minimise how much of it you pay.
- Line-shop every bet. Open the same market at two or three bookies and take the biggest number. The best-price share data shows no single bookie wins every market.
- Favour low-margin markets. Two-way and headline three-way markets beat exotic multi-outcome bets for value retention.
- Be wary of long multis. Margin compounds with every leg. A five-fold isn't paying one overround — it's paying five stacked on top of each other.
- Check the price before boosts. A 'boosted' price on a fat base margin can still be worse than a rival's standard price. Do the maths.
- Watch how prices move. When a market shortens sharply, the margin often reshuffles across outcomes; the value can sit on the side that drifted.
Run the overround calculation on a couple of your regular markets this week. Once you can eyeball a 5% market versus a 9% market, comparing SA bookies becomes second nature.
FAQ
What is a good bookmaker margin in South Africa?
Lower is better for you. From our sampled markets, margins ran from about 4.8% (10bet, 27 markets) to around 8.6% (Sportingbet, 39 markets), with Betway near 6.5% across a much larger 236-market sample. Anything in the mid-single digits on a headline two- or three-way market is competitive.
How do I calculate the overround on a betslip?
Convert each outcome's decimal odds to a percentage using 1 ÷ odds × 100, add all outcomes together, then subtract 100. The remainder is the margin. For example, 2.10 / 3.30 / 3.60 gives 47.62 + 30.30 + 27.78 = 105.70%, an overround of 5.70%.
Is the margin the same as the odds boost or bonus?
No. The margin is built into the base price of every market before any promo. A boosted price can still sit on top of a high margin, so always compare the actual number against a rival's standard price rather than assuming a boost means value.
Why do football matches have a higher margin than tennis?
Three-way football markets (home, draw, away) have more outcomes than a two-way tennis match winner, giving the bookie more room to load margin across each price. Two-way markets generally carry a tighter overround.
Does a bigger margin mean a bookie is unsafe?
Not at all. Every operator we cover is licensed by a South African provincial regulator. Margin is a pricing choice, not a safety signal. A licensed bookie can still price higher than a rival, which is exactly why comparing prices matters.
How much does margin actually cost me?
Directly, through a lower payout. On a R500 bet where a low-margin bookie prices 1.94 and a higher-margin one prices 1.85, you win R470 versus R425 on the same result — R45 gone on a single bet, before you even factor in multis where margin compounds.