Accumulators: Why Adding Selections Multiplies the Margin Against You
Accumulators promise big returns from small stakes. Here is the maths of why they are so hard to win.
Quick answer
An accumulator multiplies the odds of each selection, so returns grow quickly — but so does the chance of losing, and each leg adds its own bookmaker margin. A five-leg accumulator of 1.80 selections implies only about a 5% chance that every leg wins.
How the odds multiply
Three selections at 1.80, 2.10 and 1.65 combine to 6.24. A 10 stake returns 62.37 if all three win.
How the chances shrink
Source: Calculated from 1.80 odds per leg (55.6% implied each).
The compounding margin
If each leg carries a 5% margin, a five-fold carries far more than 5% overall. That is why accumulator promotions are so common — they are profitable products.
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Frequently asked questions
Are accumulators bad bets?
They are not mathematically worse per unit of margin by default, but margins compound and the chance of winning falls fast. Treat them as entertainment with small stakes.
What is acca insurance?
A promotion that refunds the stake (often as a free bet) if one leg loses. Read the terms.
Sources & references
- BeGambleAware — safer gambling advice www.begambleaware.org
- National Council on Problem Gambling www.ncpgambling.org
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