🎲 Probability Calculator

Single Event Probability

Probability

Two Events (A and B)

Probability

Understanding Probability

Probability measures how likely an event is to occur. It ranges from 0 (impossible) to 1 (certain). Multiply by 100 to express as a percentage.

P(A) = Favorable outcomes / Total outcomes
P(A and B) = P(A) × P(B) [if independent]
P(A or B) = P(A) + P(B) − P(A and B)

Probability Examples

  • Flipping a coin: P(Heads) = 1/2 = 0.5 = 50%
  • Rolling a 6: P(6) = 1/6 ≈ 0.167 = 16.7%
  • Drawing a red card: P(Red) = 26/52 = 0.5 = 50%

Frequently Asked Questions

What is the probability of rolling a 6 on a die? ▼
P(6) = 1/6 ≈ 0.1667 = 16.67%. A standard die has 6 faces, and only one shows 6.
What is the probability of getting heads twice in a row? ▼
P(HH) = P(H) × P(H) = 0.5 × 0.5 = 0.25 = 25%. Each flip is independent.
What does P(A or B) mean? ▼
P(A or B) is the probability that at least one of the events A or B occurs. Using the addition rule: P(A or B) = P(A) + P(B) − P(A and B).