Decimal odds — the Australian standard
Australian bookmakers quote decimal odds. The number tells you your total return per dollar staked, including your stake back:
Worked example: $10 at odds of 2.50 returns $25 in total — your $10 stake plus $15 profit. Odds of 1.50 are a "short" price (a likely outcome); odds of 6.00 are a "long" price (an unlikely one). Shorter odds = the bookmaker thinks it is more likely to happen.
Implied probability — what the price is really saying
| Decimal odds | Implied probability | Plain-English meaning |
|---|---|---|
| 1.50 | 66.7% | Expected to happen two times in three |
| 2.00 | 50.0% | A coin flip |
| 2.50 | 40.0% | Wins four times in ten, long-run |
| 4.00 | 25.0% | Wins one time in four, long-run |
| 10.00 | 10.0% | A genuine outsider |
This conversion is the single most useful skill in betting literacy. When a price says "40%", you can ask a sane question: do I actually think this happens more than four times in ten? If you cannot answer that question, you are not evaluating a bet — you are buying a feeling.
The margin — why the percentages add up to more than 100
Add the implied probabilities of every outcome in a market and you will not get 100%. You will get something like 105–108%. The excess is the bookmaker's margin (also called the overround or vig), and it is how bookmakers make money regardless of who wins.
Worked example: a tennis match priced at 1.87 for both players. Each price implies 53.5%. Together: 107%. For the bookmaker to break even on perfectly balanced action, they keep that 7% structure working for them on every market, every day. For a bettor, the lesson is blunt: at the quoted prices, the average bettor must win more often than the odds imply just to break even — against professionals whose full-time job is setting those odds.
The takeaway: you are not betting against luck; you are betting against a priced market with a margin in it. That does not make betting pointless — it makes it entertainment with a known cost, like a ticket. The moment you treat it as an income strategy, the margin starts treating you as its income strategy.
Why prices move
- Team news — a late injury or selection surprise reprices a market in seconds.
- Money flow — heavy betting on one side shortens its price and lengthens the other, balancing the bookmaker's exposure.
- New information — weather for racing and cricket, surface changes, draw releases.
A moving price is information, not an invitation. Next, learn what you are actually buying in each market: bet types, decoded.