Probability Calculator
Three tools in one: compute a theoretical probability from favorable and total outcomes, take the complement, or combine two events — independent AND or mutually exclusive OR. Every answer shows its steps.
Basic probability
Enter the number of favorable outcomes and the total number of equally likely outcomes.
P(event) = favorable ÷ total
Complement
“Not E” is everything else: subtract P(E) from 1.
P(not E) = 1 − P(E)
Combine two events
Independent AND multiplies; mutually exclusive OR adds. Pick the mode, enter both probabilities.
P(A and B) = P(A) × P(B) · P(A or B) = P(A) + P(B)