How bookmaker margins work

What a margin actually is (the overround)

Every price a bookmaker offers can be turned into an implied probability. For decimal odds the formula is simply 1 divided by the odds. If a bookmaker prices both sides of a rugby match at 1.90, each side implies a 52.6% chance (1 ÷ 1.90). Add the two together and you get 105.3% — not 100%.

That extra 5.3% is the margin, often called the overround or the "vig". A truly fair market would total exactly 100%. Anything above that is the operator's cut, spread across every outcome. The higher the total, the more the odds are shaded against you.

The key point: the margin is baked into the odds before you place a single bet. You don't pay it as a separate fee — it's the gap between the fair price and the price you're actually offered.

How to calculate the margin on any market

The method works for any number of outcomes:

• Convert each price to its implied probability: 1 ÷ decimal odds.
• Add all the implied probabilities together.
• Subtract 100%. Whatever is left over is the margin.

For a three-way football market (home / draw / away) you simply include all three prices. Say a Premiership (PSL) match is priced 2.10 (home), 3.20 (draw), 3.60 (away):

• Home: 1 ÷ 2.10 = 47.6%
• Draw: 1 ÷ 3.20 = 31.3%
• Away: 1 ÷ 3.60 = 27.8%
• Total = 106.7%

The margin here is 6.7%. On a three-way market margins are naturally a little higher than on a two-way market because the operator takes a slice out of each of the three outcomes.

A worked example: what the margin costs you

Let's price the same Test cricket contest two ways to show the effect in rands.

Bookmaker A (low margin, ~4.8%) prices two evenly matched teams at 1.98 and 1.90. Bookmaker B (higher margin, ~8.6%) prices the same two teams at 1.85 and 1.80.

Say you back the favourite with R500.

• At Bookmaker A (1.90): a winning bet returns R950, a profit of R450.
• At Bookmaker B (1.80): the same winning bet returns R900, a profit of R400.

Same outcome, same stake — R50 less profit purely because of the wider margin. Over a single bet that's a rounding error to some punters. Over 200 bets a year it compounds into a meaningful chunk of your bankroll. This is why comparing prices matters far more than any once-off sign-up perk: the margin is a cost you pay on every single ticket, not just once.

Margin figures on South African operators

We convert bookmaker prices into implied probabilities across a sample of markets and average the overround. These figures are drawn only from the samples we recorded, so treat small samples with caution.

• 10bet — average margin ~4.8% (27 markets sampled). The tightest in our sample, and it held the best price on roughly 85% of those markets.
• Betway — average margin ~6.5% (238 markets sampled). This is our largest sample and therefore the most reliable read; Betway held the best price on around 91% of markets sampled.
• Sportingbet — average margin ~8.6% (39 markets sampled). The widest of the three, and it held the best price on only about 28% of markets sampled.

The Betway sample is large enough to be genuinely representative. The 10bet and Sportingbet samples are much smaller, so the exact percentages could shift with more data — but the direction is clear: 10bet and Betway priced tighter than Sportingbet in what we recorded.

We don't have margin samples for Hollywoodbets, Supabets, Sunbet, World Sports Betting, BetXchange, LulaBet or Easybets, so we won't put a number on them. Compare their live odds yourself before committing.

Why margins differ between markets and operators

Margins aren't fixed across a site. A few patterns hold true almost everywhere:

• Big, liquid markets are tighter. A Premier League match winner or a Champions League final will carry a slimmer margin than an obscure lower-division fixture, because competition between operators forces prices closer to fair.
• Multi-outcome markets are wider. First goalscorer, correct score and outright futures odds carry chunky margins because there are many outcomes to load.
• Live betting can widen margins. In-play prices move fast and operators build in extra cushion to protect against sudden swings.
• Accumulators multiply the margin. Each leg of a multi carries its own overround, and those stack. A five-leg bet built from 6% markets carries far more embedded margin than any single leg.

How to reduce the margin you pay

You can't remove the margin, but you can pay less of it:

• Line-shop the same bet across several licensed SA operators before staking. The price difference is the margin difference.
• Focus on high-liquidity markets — top-flight football, ATP and WTA tennis, Test cricket, UFC main events — where prices are keenest.
• Be wary of long accumulators if you care about value; the stacked margin is the reason they pay so rarely.
• Treat cash out as a convenience, not a value tool — the operator applies its margin to the buy-back price too.

A punter who consistently takes the best available price on liquid markets is effectively betting into a lower average margin than someone who bets everything with one operator out of habit.

Margin versus safety: don't optimise the wrong thing

A tight margin is worthless if you can't withdraw. All the operators referenced here hold provincial licences — 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; and Easybets under the Mpumalanga Economic Regulator. South African betting is regulated provincially under the National Gambling Board framework, and the legal minimum age is 18.

Weigh margin against licence safety, payout speed and payment options. Sportingbet, for example, carries a wider margin in our sample but offers 0–24h withdrawals; a slower-paying, lower-margin operator might suit a value-focused punter better. Decide what you're optimising for before you sign up.