Double and treble bets
A double is a single bet on two selections and a treble a single bet on three, where every selection must win for the bet to pay out. The returns from the first leg roll on as the stake for the next, so the odds multiply together. That multiplication is the whole attraction, and it is also the reason one losing leg sinks the lot.
How a double and treble are calculated
Convert each price to decimal odds and multiply them. A €10 double on a 2/1 shot and a 6/4 shot gives 3.0 × 2.5 = 7.5, so the bet returns €75, stake included.
Add an even-money third leg and the treble becomes 3.0 × 2.5 × 2.0 = 15.0, returning €150 from the same €10. The implied probability shrinks just as fast: 33.3% × 40% × 50% comes to roughly 6.7%, and that is before the bookmaker’s margin, which compounds on every leg you add.
A void leg, such as a non-runner, is usually settled at odds of 1.0, so a treble drops to a double rather than losing, though settlement rules on dead heats and Rule 4 deductions vary between bookmakers and are worth reading on the site you use.
What a treble is often confused with
The common mix-up is between a treble and a trixie. A trixie takes the same three selections but splits them into four bets: three doubles plus the treble, so a €10 unit stake costs €40 and two winners still return something.
On a bet slip you will also see “doubles” listed as a separate line, which means every possible pair, each staked on its own.
Neither should be confused with a double result market, which is a single bet on the half-time and full-time outcome of one match.
