Gambling terms, explained straight

Odds, Probability & Bankroll

Odds vs probability in statistics

Probability measures the chance an event occurs out of all possible outcomes; odds compare the chance it occurs to the chance it does not.

Formula
Odds = p / (1 − p), where p is probability3
Example
If p = 0.50, odds = 1.002
Interpretation
Odds below 1 mean the event is less likely than not3

Key points

  • Probability is an absolute measure (successes out of total); odds are a relative measure (successes vs failures).1
  • In statistics, odds are used for binary events and in clinical comparisons, not just betting.4
  • Betting odds are a market format; statistical odds are the pure event/not-event ratio.1

Where this term is used

Not the same as

  • Betting odds to probability — a conversion method that turns market odds into implied probability, whereas odds vs probability explains the conceptual difference between the two measures
Odds & probability Odds vs probability Explains the core difference between odds and probability as statistical measures. Odds & probability Decimal odds to probability Shows how to convert decimal betting odds into implied probability. Odds & probability Odds vs probability formula Presents the mathematical formulas for odds and probability side by side. Odds & probability Odds Defines odds as a ratio of event to non-event in statistics and betting. Odds & probability Betting odds Explains how odds are used in gambling to represent payout and implied likelihood. Odds & probability American odds to implied probability Converts American moneyline odds into implied probability percentages.

Sources

  1. 3.10 Odds | Probability, statistics, and the likelihood ratio ... lrcfs-ap2.dundee.ac.uk Defines odds as a relative measure of uncertainty and distinguishes it from probability.
  2. LibGuides: Quantitative data collection and analysis: Probability libguides.tees.ac.uk Provides the example that when p=0.50, odds equal 1.00.
  3. Odds en.wikipedia.org Gives the odds formula and states that odds below 1 mean the event is less likely than not.
  4. The odds ratio - PMC - NIH pmc.ncbi.nlm.nih.gov Explains that odds apply to binary events and clinical comparisons beyond betting.

Sources are drawn from regulators, universities and published research, and each one is labelled with what it actually is — a preprint is not called a paper. Bookmaker and affiliate pages are never cited here, because a page that sells betting is not a neutral authority on it.

Written and maintained by Ellis Warrender, writer and maintainer.

Last updated 28 July 2026. Spotted an error? Tell me and it gets fixed and logged on the corrections page.