Odds against means a price longer than even money: in Australian decimal odds, anything above $2.00. A winning bet at odds against makes more profit than its stake, because the market rates the outcome less likely to happen than not. At an illustrative $3.20, a $25 bet returns $80, which is $55 profit, and the price implies 1 / 3.20 = 31.25%.
In fractional odds the same price is 11/5, said "eleven to five against". How betting odds work shows how any price turns into a return and a chance.
How odds against reads in fractional odds
A fraction puts the profit first and the stake second, so 11/5 wins $11 for every $5 staked. At odds against the first number is always the bigger one. To convert, add 1: decimal odds = fraction + 1, so 11/5 = 2.2 + 1 = $3.20. With illustrative prices:
| Fraction | Said as | Decimal | Implied chance |
|---|---|---|---|
| 11/10 | Eleven to ten against | $2.10 | 47.6% |
| 11/5 | Eleven to five against | $3.20 | 31.25% |
| 7/2 | Seven to two against | $4.50 | 22.2% |
| 9/1 | Nine to one against | $10.00 | 10.0% |
| 16/1 | Sixteen to one against | $17.00 | 5.9% |
Working for 7/2: 7 / 2 + 1 = $4.50, and 1 / 4.50 = 22.2%. Said without the word "against", "seven to two" means the same price.
Why odds against implies under 50%
Implied probability = 1 / decimal odds, and 1 divided by any number over 2 is less than 0.5. The nearer a price sits to $2.00, the nearer its chance sits to a coin toss: $2.10 implies 47.6%, while $17.00 implies 5.9%. Even money, $2.00 and 50%, is the dividing line.
Those chances still carry the bookmaker's margin, so the fair chance is lower again. A favourite can be odds against too. In an illustrative three-way soccer market of $2.45, $3.30 and $2.90, every outcome is odds against, because the draw takes its share: 40.8% + 30.3% + 34.5% = 105.6%.
Odds against vs odds on
Turn a fraction upside down and you cross to the other side of even money. 7/2 against ($4.50) implies 2 / 9 = 22.2%. Flip it to 2/7, which is odds-on at $1.29 and said "seven to two on", and it implies 7 / 9 = 77.8%. The two add up to exactly 100%, because they price one contest from opposite sides with no margin in either.
A bookmaker would shade both sides instead, quoting something like 3/1 and 1/4. Those imply 25% and 80%, a 105% book (illustrative prices).
Mistakes with odds against prices
With illustrative prices and a $10 stake:
| Mistake | What it costs | The fix |
|---|---|---|
| Reading 2/7 as 7/2 | It returns $12.86, not the $45 you expected | Bigger number first means odds against |
| Calling any odds-against price unlikely | $2.10 still implies 47.6%, almost a coin toss | Read the implied chance, not the label |
| Leaving the stake out of a fractional return | 11/5 returns $32, not $22 | Decimal = fraction + 1 |
Following an odds-against price on the Terminal
Price history (flucs) on B337's Terminal shows how each price has moved, so you can see whether an odds-against runner is drifting further out or firming towards even money. The Terminal lines up prices from 40+ bookmakers across racing and sports, and decimal odds explained covers reading each one.
Prices are read on a repeating cycle and can trail a bookmaker's own, so confirm a price in your account before you bet. A free account opens a limited view of the Terminal with live odds.
Risk: Betting involves risk. An odds-against bet is priced to lose more often than it wins, long losing runs are normal at long prices, and there is no guarantee of profit. See responsible gambling for limits and support.