What this calculator does
Probability expresses how likely an event is. This calculator gives a single-event probability and the chance of seeing at least one success over repeated independent trials.
Formula used
Single probability equals successful outcomes divided by total outcomes. At least one success equals one minus the probability of no success across all trials.
How to read the result
Repeated-trial results assume each trial is independent and has the same probability. That is true for many dice-style examples, but not every real situation.
Assumptions
- Successful outcomes cannot exceed total outcomes.
- Trials are independent.
- Probability remains the same on each trial.
Sources and checks
This calculator uses a standard public formula. Where rules or thresholds can change, source links are listed on the relevant page.
Frequently asked questions
What does at least one mean?
It means one or more successes. For repeated trials, it is often easier to calculate one minus the chance of getting no successes.