How Accumulator Odds Are Calculated — The Multiplication Rule

The Mathematics of Accumulator Betting

An accumulator (or multibet) combines multiple selections into a single bet. All selections must win for the bet to pay out. The combined odds are calculated using the multiplication rule.

The Formula

Combined Odds = Odds₁ × Odds₂ × Odds₃ × ... × Oddsₙ

Example: 3-Leg Accumulator

LegMatchOddsRunning Combined |-----|-------|------|-----------------| 1Arsenal to win2.002.00 2Barcelona to win1.803.60 3Man City to win2.509.00

A KES 500 stake at combined odds of 9.00 returns KES 4,500 (profit of KES 4,000).

Probability Decay

Each leg multiplies the probability of winning:

Combined Probability = P₁ × P₂ × P₃ × ... × Pₙ

Using the example above (assuming fair odds):

After Leg 1: 50% probability

After Leg 2: 50% × 55.6% = 27.8%

After Leg 3: 27.8% × 40% = 11.1% combined probability

This is why accumulators are high-risk: the probability of winning decreases with every additional leg.

Use our Multibet Calculator to calculate combined odds and see the probability decay visualization for up to 20 selections.