Probability Calculator

Estimating how likely something is becomes straightforward here, whether the question is broad or personal. Picture weighing the odds a forecaster assigns to next year's economic growth, or sizing up your chances of drawing a winning raffle ticket—the same underlying logic applies. Anyone who reasons from data, from business strategists to students, can put it to work.

The engine rests on a few core formulas. For a single event, probability P equals the number of favorable outcomes divided by the total number of possible outcomes. When two events A and B are independent, their joint probability is P(A and B) = P(A) * P(B). When A and B are mutually exclusive, the chance that either occurs is P(A or B) = P(A) + P(B). For independent events the calculator also gives P(A or B) = P(A) + P(B) - P(A) × P(B), and for mutually exclusive events it sets P(A and B) to 0. Every result is shown as a decimal, a percentage, a fraction and odds.

Single-event accuracy hinges on counting outcomes honestly—every favorable case and every possible case must be accounted for. With combined events, the key distinction is whether they are independent, meaning one has no bearing on the other, or mutually exclusive, meaning they cannot both happen at once. Reaching for the independent-events formula when the events are actually mutually exclusive is a classic error that quietly corrupts the answer.