When an Australian bookmaker lists a price of 2.10, it is telling you two things at once: what you will receive if your selection wins, and how often the bookmaker thinks it will win. The first part is arithmetic; the second is the bookmaker's estimate of chance, expressed as a price instead of a percentage. Everything else in this guide — formats, conversions, implied probability — is a way of reading those two numbers without guessing.
Decimal odds: the Australian default
Decimal odds are the format used across almost all licensed Australian wagering operators, and they are the most direct: the number is the total return per unit staked, including your original stake. A $20 stake at 2.10 returns $42.00 (your $20 back plus $22.00 profit) if the selection wins. The profit alone is the price minus one, so a 2.10 price pays $1.10 profit per dollar. Favourites sit below 2.00 — a price of 1.40 pays only $0.40 profit per dollar, which is why a heavy favourite's price looks so unexciting — while long shots run to 10.00, 20.00 and beyond, where a small stake can return a large sum. Or, more often, a small stake returns nothing.
Because the number doubles as a probability machine, decimals make comparing prices effortless. You can read three different bookmakers' boards in the same format, and you can do the implied-probability math with one division. That is why, when a fixture is listed in fractional odds in one place and decimal in another, converting to decimal first is the cheapest way to make sure you are actually comparing prices.
Fractional odds: the traditional Australian voice
Fractional odds — 6/1, 5/2, 1/2 — are the format Australian bettors grew up with, and they still dominate the racing markets and much of the football coverage. The top number is the profit; the bottom number is the stake required to earn it. At 6/1, a $10 stake wins $60 profit; at 5/2, $10 wins $25 profit; at 1/2, $10 wins $5 profit. The format has a real ergonomic advantage for racing bettors: a price of 6/1 instantly reads as "six-to-one", a statement about rank in the field, not just a payout. Converting to decimal is mechanical: divide the top by the bottom and add one. 6/1 becomes 7.00, 5/2 becomes 3.50, 1/2 becomes 1.50.
One trap worth knowing: fractional prices have no natural zero point for "even money" in everyday speech. "Even" is 1/1 — one unit of profit on one staked — which is exactly 2.00 decimal. When a pundit says a team is "the even-money favourite", they mean it prices to double your stake back if it wins, not that the match is fifty-fifty in a moral sense. It is a price, and like all prices it reflects what the market believes, plus the bookmaker's margin.
American moneyline: the imported format
Moneyline odds, with their plus and minus signs, come from North American sportsbooks and appear on Australian boards for a minority of markets, usually imported US or North American lines. The convention is backwards depending on the sign. A minus price (−120) is a favourite: it tells you how much you must stake to win $100 profit, so −120 means stake $120 to win $100. A plus price (+150) is an underdog: it tells you the profit on a $100 stake, so +150 wins $150 profit on $100. Even money is +100, which is 2.00 decimal or 1/1 fractional.
The conversions are fixed fractions, not estimates: a negative price converts to decimal by adding 100 and dividing — −120 becomes 220/100 = 2.20; a positive price converts by dividing by 100 and adding one — +150 becomes 2.50. Keep these two formulas in your head and the imported lines stop being a separate universe.
Implied probability: the probability inside the price
Every decimal price encodes a probability: divide 100 by the price. A 2.00 price implies 50%, 4.50 implies about 22.2%, 1.50 implies about 66.7%. The same trick works the other way on the other formats — a 6/1 fractional price (7.00 decimal) implies roughly 14.3%, and a +150 moneyline (2.50 decimal) implies 40%. Read the board this way and you stop seeing numbers and start seeing the bookmaker's whole forecast of the event, laid out market by market.
There is one honest caveat, and it is important: the implied probabilities of all outcomes in a market will add up to more than 100%. On a two-way football market you might see 1.90 against 1.95 — 52.6% plus 51.3%, or 103.9%. The excess above 100% is the bookmaker's margin, the built-in cost of every price on the board. It means "implied probability" is a fair, comparable estimate of chance, not a promise: no price tells you how often an outcome will actually happen, and no set of prices is a forecast you can treat as a plan. The margin is why two identical books at different prices are worth different things, and why comparing the decimal number remains the fastest sanity check before you place anything.
Worked examples across all three formats
Five prices, the same chance written three ways. Use this as a reference while you are still building the habit of converting before you compare.
| Decimal | Fractional | American | Profit on $10 | Implied probability |
|---|---|---|---|---|
| 1.50 | 1/2 | −200 | $5.00 | ≈ 66.7% |
| 2.00 | 1/1 | +100 | $10.00 | 50% |
| 2.50 | 5/2 | +150 | $15.00 | 40% |
| 3.00 | 2/1 | +200 | $20.00 | ≈ 33.3% |
| 7.00 | 6/1 | +600 | $60.00 | ≈ 14.3% |
Two habits make the whole system pay for itself. First, convert anything not shown in decimal to decimal before you decide — one division, never a guess. Second, read the implied probability out loud when a price looks attractive: if a 4.50 underdog implies 22% and your honest read of the fixture is "maybe 20%", the price is not offering you an opportunity, it is offering you a story. The numbers on the board are the bookmaker's view of the event with a margin on top; your job is to know where you disagree, and to stay small enough that being wrong is the price of entertainment.