Probability Calculator

How it works

Probability counts favourable outcomes against all equally likely outcomes: P = favourable ÷ total. One face of a die is 1/6 ≈ 0.167 or 16.7%; drawing a heart from a full deck is 13/52 = 0.25. The scale is bounded: 0 means impossible, 1 means certain, and nothing can lie outside. That is a useful sanity check — a result above 1 always means a mistake, usually counting the same outcome twice or using a total that is too small. The complement rule saves a lot of effort: P(not A) = 1 − P(A). Computing "at least one" is often far easier as 1 minus the probability of none. And a caution the formula hides: it assumes every outcome is equally likely, which holds for fair dice and shuffled cards but not for real-world events like weather or illness.