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How to read betting odds

Decimal, fractional, and American odds explained. How to convert formats, calculate implied probability, and spot value.

TM
Thabo Mokoena • Editor • Fact-checked by Lerato Dlamini

Decimal odds

Decimal odds are the default format on all major South African bookmakers. The number represents your total return for every R1 staked, including the return of your original stake.

Odds R100 stake returns Profit What it means
1.20 R120 R20 Heavy favourite
1.80 R180 R80 Moderate favourite
2.00 R200 R100 Evens (50/50)
3.50 R350 R250 Underdog
10.00 R1,000 R900 Long shot

The formula for profit from decimal odds is: profit = (odds − 1) × stake. So odds of 3.50 on a R200 bet: (3.50 − 1) × R200 = R500 profit, total return R700.

Fractional odds

Fractional odds are common in UK horse racing and some international sportsbooks. They show profit relative to stake, not total return. The number on the left is profit; the number on the right is the stake required to earn that profit.

Fractional Decimal equivalent R100 profit
1/5 1.20 R20
4/5 1.80 R80
Evens (1/1) 2.00 R100
5/2 3.50 R250
9/1 10.00 R900

To convert fractional to decimal: divide the numerator by the denominator, then add 1. So 5/2 = (5 ÷ 2) + 1 = 3.50. Use the Bonus Browser Betting Calculators Betting Guides

Odds Converter to do this instantly.

American odds

American odds (also called moneyline odds) use a +/- system based on a R100 unit. They're rarely used on SA platforms but appear on US-focused content and some international odds comparison sites.

  • Negative number shows how much you must stake to win R100 profit. -150 means stake R150 to profit R100.
  • Positive number shows how much profit a R100 stake returns. +250 means a R100 stake profits R250.

The crossover point is +100 and -100, which both equal decimal odds of 2.00 (evens).

Implied probability

Implied probability is the probability of an outcome winning as implied by the odds before bookmaker margin is removed. It's the most useful number for comparing whether a price represents value.

Implied probability (decimal odds) = 1 ÷ odds

Odds 2.50 = 1 ÷ 2.50 = 0.40 = 40%
Odds 1.60 = 1 ÷ 1.60 = 0.625 = 62.5%
Odds 4.00 = 1 ÷ 4.00 = 0.25 = 25%

When you add the implied probabilities of all outcomes in a market (for example, home win + draw + away win in football), the total will exceed 100%. That excess is the bookmaker's margin. If the total is 106%, the margin is 6%.

Finding value

Value betting means placing bets where you believe the true probability of an outcome is higher than the bookmaker's implied probability. If you think a team has a 50% chance of winning but the bookmaker prices them at 2.20 (implying 45.5%), there's a theoretical edge.

This is harder than it sounds. Bookmakers employ professional odds compilers and have extensive data. But on less-watched markets, local knowledge can help. SA bettors who follow Currie Cup or Diski Challenge closely may spot mispriced lines before the market adjusts.

The key habit is converting odds to implied probability and asking: "Do I genuinely believe this outcome is more likely than the bookmaker does?" If you can't honestly answer yes, the price isn't value.

SA sports examples

Here are three examples using South African sports to practise reading odds.

Example 1: Springboks vs All Blacks (Rugby)

Springboks 2.10 / Draw 18.00 / All Blacks 1.75

All Blacks are the favourite at 1.75 (implied 57.1%). Springboks at 2.10 imply 47.6%. Combined with draw: 47.6 + 5.6 + 57.1 = 110.3% total, meaning the market carries a 10.3% margin. This is higher than typical for a major Test and worth shopping around.

Example 2: Kaizer Chiefs vs Orlando Pirates (PSL Football)

Chiefs 2.40 / Draw 3.10 / Pirates 2.80

Implied probabilities: 41.7% + 32.3% + 35.7% = 109.7%. The draw at 3.10 implies a 32.3% chance. PSL derbies draw roughly 28-30% of the time historically, so the 3.10 is at or below fair value.

Example 3: Proteas to win a Test series (Cricket outright)

Proteas 1.65 / Draw/No result 4.50 / Opposition 2.90

Proteas at 1.65 imply a 60.6% win probability. A R100 bet returns R165. If you think Proteas win 70%+ of such series at home, this price has positive expected value.

Frequently asked questions

Almost all licensed SA bookmakers display decimal odds by default. Some horse racing platforms also show fractional odds. American odds are rare on SA platforms but appear on international content and some US-focused markets.
Profit = (odds − 1) × stake. So at odds of 3.20 with a R100 stake: (3.20 − 1) × R100 = R220 profit. Your total return including the stake back is R320.
Implied probability is the probability of an outcome winning as implied by the odds, before bookmaker margin is removed. For decimal odds, it is 1 divided by the decimal odds. Odds of 2.50 imply a 40% chance of winning (1 ÷ 2.50 = 0.40).
Divide the top number by the bottom number, then add 1. So 5/2 becomes (5 ÷ 2) + 1 = 3.50 in decimal. Use the Bonus Browser Betting Calculators Betting Guides Odds Converter to do this automatically for any format.