What Is Return on Investment in Gambling?

Ingrid Pastore
Last updated March 27, 2026, 12:11 PM
  • Strategy

Probability in gambling is the mathematical likelihood of a specific outcome occurring in a game or bet. It determines the chances of winning or losing and is expressed as a fraction, decimal or percentage. For Australian players, understanding probability helps assess game fairness and long-term expectations in licensed online casinos, where outcomes are governed by random number generators and published rules.

Probability

How Probability Determines Game Outcomes

Every casino game has fixed probabilities based on its rules. In roulette, the probability of landing on red is 18/37 or about 48.6% on a European wheel. Video slots use random number generators to ensure each spin’s outcome is independent, with probabilities set by the paytable and reel configuration.

Why Probability Matters to Players

Probability reveals the house edge, showing the casino’s built-in advantage over time. Higher probability events pay less, while rare outcomes offer bigger payouts. Players use it to compare games, though short-term results vary due to randomness. In Australia, regulators require transparent probability disclosure in licensed games.

Game TypeExample OutcomeProbability
European RouletteRed/Black48.6%
Video SlotsAny Win20-30%
BlackjackPlayer Win42-48%
Dice RollEven Number50%

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