Math & Science
Probability Calculator
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Calculate probability for single events, AND, OR, and complement. Supports independent and dependent events with formula display. Free, instant, no signup.
Calculation type
Quick reference
P(not A) = 1 − P(A) — complement rule
P(A ∩ B) = P(A) × P(B) — independent events only
P(A ∪ B) = P(A) + P(B) − P(A ∩ B) — addition rule
How to Calculate Probability (2026)
How to Calculate Probability — free online tool and guide with examples.