Basic Probability Calculator
Calculate the probability of an event given favorable and total outcomes
About this calculator
Probability = Favorable outcomes / Total outcomes. Rolling a 3 on a die: 1 favorable outcome, 6 total → probability 1/6 ≈ 0.167 or 16.7%. Probability ranges from 0 (impossible) to 1 (certain). This is classical probability, assuming all outcomes are equally likely.
How to use
Drawing a red card from a standard deck: 26 red cards out of 52 total → 26/52 = 0.5 = 50% probability.
Frequently asked questions
What is the difference between probability and odds?
Probability is favorable/total. Odds is favorable/unfavorable. A probability of 1/4 means odds of 1:3 (1 favorable, 3 unfavorable). Bookmakers use odds; mathematicians use probability.
What does independent probability mean?
Two events are independent if one does not affect the other. Flipping heads twice: P(heads) × P(heads) = 0.5 × 0.5 = 0.25. The first flip does not influence the second.