Simple Probability Calculator
Enter the number of favorable outcomes and total possible outcomes to get the probability as a percentage and the odds against.
Simple Probability Calculator
Calculates the probability and odds of a favorable outcome from the total number of possible outcomes.
This calculator applies the basic classical probability formula — favorable outcomes divided by total possible outcomes — to give you both a percentage probability and the equivalent 'odds against' ratio that's common in games and betting contexts. It assumes all outcomes are equally likely, which fits situations like drawing cards, rolling dice, or picking from a set of equally weighted options. Use it for quick probability homework checks or to sanity-check odds you see quoted elsewhere.
Example
- With the default values shown above, this calculator returns: Probability ≈ 7.69%; Odds Against (to 1) ≈ 12 to 1.
Frequently Asked Questions
What's the difference between probability and odds?
Probability is favorable outcomes divided by total outcomes (expressed as a percentage), while odds against compares unfavorable outcomes to favorable ones, e.g. '12 to 1'.
What's a real example?
With the default values (4 favorable outcomes out of 52, like drawing an ace from a standard deck), the probability is about 7.69% and the odds against are 12 to 1.
Sources
- Standard formula, publicly documented method