The Combined Odds calculator determines the fair odds for at least one of your selections winning. This is useful for multi-bet promotions where you need ANY one bet to win (not all of them).

When to use it

Use the Combined Odds calculator when evaluating:

• "Get a bonus bet if at least one of your 3+ bets wins"
• "Refund if none of your multi-bets win" (inverse - you can calculate the odds of this happening)
• Assessing the value of insurance promotions on multis
• Building hedging strategies for accumulators

How it works

The calculator uses probability theory to determine the chance that at least one selection wins:

1. It calculates the probability each selection loses
2. Multiplies those probabilities to get the chance ALL selections lose
3. The chance at least one wins = 1 - (chance all lose)
4. Converts this probability back to decimal odds

Understanding the inputs

For each selection, you enter:

• Odds: The decimal odds for that selection to win

You can add up to 10 selections using the "Add selection" button. Each selection shows its implied probability percentage next to the odds input.

Understanding the outputs

The calculator displays:

1. Combined Odds: The fair odds that at least one of your selections wins. This is the key output.
2. Implied Probability: The percentage chance that at least one selection wins.

Practical example

A bookmaker offers "Get $20 bonus bet back if at least one of your 4 Saturday bets wins". The fair odds for your four selections are:

• Geelong at 1.80
• Richmond at 2.20
• Carlton at 3.00
• Collingwood at 1.65

Enter these four odds into the calculator.

The calculator shows:

• Combined Odds: 1.07
• Implied Probability: 93.63%

This means there's a 93.63% chance at least one of your bets wins (only a 6.37% chance all four lose). The promotion is essentially giving you a ~94% chance to get your $20 bonus bet.

Comparing to "all win" promotions

This calculator is equivalent to the 1 or more wins of the X out of N calculator:

• Combined Odds: Calculates odds of at least one win (1 or more wins)
• X out of N: Calculates odds of X or more wins out of N selections

Use Combined Odds when the promotion cares about ANY win. Use X out of N when the promotion requires a specific number of wins.

Common issues

The combined odds seem too low (close to 1.01). Is this correct?

Yes, if you have many selections, even relatively long-odds ones, the probability that at least one wins approaches 100%. For example, 10 selections at 3.0 odds each give you a 98.3% chance of at least one winning (combined odds of 1.02). This is why "at least one win" promotions are often very valuable.

Can I use this for multi betting?

Not directly. This calculator is for "at least one wins", which is the opposite of a multi where ALL must win. For multi odds, just multiply the individual odds together: Multi Odds = Odds₁ × Odds₂ × Odds₃ × ... × Oddsₙ.