Decimal odds: reading prices like a bookmaker

01The arithmetic

Return equals stake times odds. R100 at 2.50 returns R250 - your R100 stake plus R150 profit. R100 at 1.40 returns R140 (R40 profit); R100 at 8.00 returns R800 (R700 profit). Implied probability is one divided by the odds: 2.50 implies 40%, 1.40 implies 71.4%. When you estimate a team's chance higher than the implied probability, you have found what bookmakers call value - and what long-term winners call the only bet worth placing.

02The margin, exposed

Add the implied probabilities across every outcome of a market and you get more than 100%; the excess is the bookmaker's margin. A football 1X2 at 2.10 / 3.40 / 3.60 implies 47.6% + 29.4% + 27.8% = 104.8%, a 4.8% margin. Two-outcome markets near even money run tighter margins than long-shot-heavy markets. A serious odds shopper's whole job is buying the same contract at lower margin - one decimal point of price is worth more than any tip.

03Margin hunting in practice

Pick one Saturday fixture and price it at Apex Bets and at two established SA bookmakers. Note each market's overround (the 104.8% figure above). Over ten fixtures you will know which book prices your sport cheapest. Do the same exercise on accumulators, and you will see why margin multiplies per leg - a five-leg acca at 105% per leg prices at roughly 127% overround, which is the mathematical answer to why accas feel exciting and behave expensively.