Accumulator odds explained
Accumulator odds multiply, and so does the bookmaker's margin. A real four-fold from tonight's BAI8 cards shows why a long acca usually costs more than it pays.
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Accumulator odds are the prices of every leg multiplied together, and every leg has to win. That is why the payout looks big: four legs at around 2.2 each pay about 26 to 1. The catch is that the bookmaker's margin multiplies too. If each leg is priced a little short of its real chance, the whole accumulator is priced a lot short. On tonight's BAI8 cards, a four-fold of our picks would pay 25.93 for a bet we think lands about 2% of the time.
How the odds multiply
Take the four negative-edge cards on the Desk this week: Real Betis, Borussia Dortmund, Juventus and Getafe, all at their best quoted price.
| Leg | Best price seen | Our chance | Expected return per 1 staked |
|---|---|---|---|
| Real Betis | 2.27 | 36.8% | −0.16 |
| Borussia Dortmund | 2.14 | 37.8% | −0.19 |
| Juventus | 2.11 | 38.6% | −0.19 |
| Getafe | 2.53 | 36.3% | −0.08 |
| Four-fold | 25.93 | 1.95% | −0.49 |
The four-fold price is 2.27 × 2.14 × 2.11 × 2.53 = 25.93. Our chance that all four win is 36.8% × 37.8% × 38.6% × 36.3% = 1.95%, a fair price of about 51. Each single loses between 8 and 19 pence per pound on our numbers. The four-fold loses 49. Expected return is explained properly in expected value in betting in plain numbers.
Compounding works both ways
The same arithmetic applies to legs with a positive edge. Tonight's two Championship cards are Southampton at 3.10 (we have 38.0%) and Sheffield United at 2.88 (we have 36.8%).
| Leg | Best price seen | Our chance | Expected return per 1 staked |
|---|---|---|---|
| Southampton | 3.10 | 38.0% | +0.18 |
| Sheffield United | 2.88 | 36.8% | +0.06 |
| Double | 8.93 | 14.0% | +0.25 |
On our estimates the double has a bigger edge than either single. But that figure is only as good as our two chances. If each is a few points too high, the error multiplies in exactly the same way, and the double is far more likely to lose than to win: about six times in seven. These are estimates, not promises.
Why stake size matters more here
A bet that wins one time in fifty, or one in seven, produces long losing runs even when it is fairly priced. Sizing it like a single is how a bankroll goes, which is the subject of staking without going broke and how long a losing run can honestly last.
What this does not tell you
It does not tell you any of these legs will win, or that the double is a bet to place. It also assumes the games are independent. Bookmakers often refuse or reprice accumulators whose legs are linked, and real quotes move before kick-off.
18+. Bet only what you can afford to lose.
Common questions
How are accumulator odds calculated?
Multiply the decimal prices of every leg. Four legs at 2.27, 2.14, 2.11 and 2.53 make 25.93. Every leg has to win for the bet to pay.
Why do accumulators usually lose money?
Because the margin on each leg multiplies too. If each leg is a little short of fair, the whole bet ends up a lot short of fair.
Can an accumulator ever have a positive edge?
Only if every leg does. On our estimates, two positive-edge legs combined have a bigger edge than either alone, but any error in those estimates also compounds.
What is the chance an accumulator wins?
Multiply the chance of each leg. Four legs at about 37% each give roughly a 2% chance that all four win.