Guide · Updated 23/05/2026 · iGaming Reviews
Betting odds, explained
This guide covers the three odds formats you will see, how to convert any odds into implied probability, what the over-round (the bookmaker’s margin) actually costs you, and how to spot a value bet in the wild. Plain English, real SA examples, no PhD required.
The three odds formats
Same bet, three ways to write the price. South African sportsbooks use decimal by default, but you will see all three when watching UK or US streams.
Decimal odds
The SA default. The number is your total return per R1 stake, including your stake back. So 2.50 means R1 returns R2.50.
R100 stake at 2.50 = R250 back (R150 profit)Fractional odds
UK pubs and SA horse racing forms. 5/2 means R5 profit per R2 staked. To convert: divide and add 1. 5/2 = 3.50 decimal.
R100 at 5/2 = R250 profit + your R100 stake backAmerican odds
NBA, NFL and US sportsbooks. +250 means R100 wins R250 profit. -150 means stake R150 to win R100. Rare in SA.
+250 = 3.50 decimal | -150 = 1.67 decimalFrom odds to implied probability
The most useful skill in betting is converting any odds into a percentage probability. The formula for decimal odds is one bit of school maths:
Implied probability % = 1 / decimal odds × 100
| Decimal odds | Implied probability | Real-world example |
|---|---|---|
| 1.10 | 91% | Heavy favourite, almost certain |
| 1.50 | 67% | Strong favourite |
| 2.00 | 50% | Coin flip / even money |
| 3.00 | 33% | Underdog |
| 5.00 | 20% | Long shot |
| 10.00 | 10% | Outsider |
| 50.00 | 2% | Lottery odds territory |
Once you know the implied probability, you can ask the only question that matters: do I think this event is more or less likely than the odds suggest? If you think Manchester City beats Arsenal 70% of the time and the odds are 2.00 (50% implied), the bookmaker is offering you value. If your estimate is 40% and they are at 2.00, they are not.
The over-round (the margin)
If you add up the implied probabilities of every outcome in a market, you do not get exactly 100%. You get more. The amount over 100% is the over-round, and it is how the bookmaker makes money.
Example, a 1X2 market priced as:
- Home 2.20 (45.5%)
- Draw 3.40 (29.4%)
- Away 3.30 (30.3%)
Total: 105.2%. The 5.2% over-round is the bookmaker’s expected margin on the market. If they took balanced action on all three outcomes, they would keep 5.2% of total stakes regardless of the result.
Typical over-rounds in South Africa
Margins vary by sport, market and operator. The general pattern at SA sportsbooks:
| Market | Typical over-round | Why |
|---|---|---|
| Top European football 1X2 | 4 to 6% | High volume, competitive market |
| Top European football BTTS | 6 to 8% | Lower volume sub-market |
| SA Premiership 1X2 | 6 to 9% | Local market, less competitive pricing |
| Lower league football | 10 to 15% | Trader uncertainty, low volume |
| Player props | 10 to 20% | High variance, hard to price |
| Lucky Numbers (1 from 49) | 20 to 30% | Lottery-style product |
| Slot RTP equivalent | 3 to 8% | Casino games are tighter |
The implication: if you want a fair shot, stick to high volume markets where the margin is small. Avoid low volume props and lottery-style products unless you are doing it for fun, not for profit.
How to spot value
A value bet is one where your honest estimate of the probability is higher than the implied probability of the odds. Three reliable approaches:
1. Line shopping
The same match is priced differently across different sportsbooks. If Hollywoodbets has Manchester City at 1.80 but Gbets has them at 1.95, the second is the better bet for the same outcome. Over a season, the difference between best price and worst price is often 5 to 10%, more than the margin itself.
2. Closing line value (CLV)
Compare the odds you took with the closing odds (the final price right before kickoff). If you regularly bet at higher odds than the closing line, you are likely a profitable bettor in the long run, even on bets that lose. The closing line is the sharpest estimate of true probability.
3. Specific knowledge
If you genuinely know more than the average punter about a niche league or a specific team’s form, you can find value the bookmaker has not priced. Most casual bettors do not have this edge in the markets they bet on. Being honest about that beats fooling yourself.
Bankroll basics
Even good bettors lose 40% of the time. To survive variance, never stake more than 1 to 3% of your bankroll on a single bet. A R10,000 bankroll means R100 to R300 max per bet. This is boring advice but it is what separates people who quit after a bad weekend from people who can play long term.
Compare SA sportsbooks
Margins, market depth, live odds and bonus value are all in our reviews. The lower the over-round, the better the long term value for you.
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