How is basic probability calculated?

Probability = favorable outcomes ÷ total possible outcomes.

How is probability calculated for independent events?

Multiply the individual probabilities together.

What's the difference between independent and dependent events?

Independent events don't affect each other's outcome; dependent events do.

Probability Calculator - Two Event Probability Calculator

Probability Calculator

Calculate combined probabilities for two independent events — AND, OR, and complement.

Probability of Event A (0 to 1)

Probability of Event B (0 to 1)

P(A and B) — both happen-

P(A or B) — at least one happens-

P(not A)-

P(not B)-

What Is Probability?

Probability measures how likely an event is to happen, expressed as a number between 0 (impossible) and 1 (certain). This calculator handles two independent events — where the outcome of one doesn't affect the other, like flipping a coin and rolling a die.

Formulas

P(A and B) = P(A) × P(B)

P(A or B) = P(A) + P(B) - P(A) × P(B)

P(not A) = 1 - P(A)

How to Use This Calculator

Enter the probability of Event A as a decimal between 0 and 1 (e.g. 0.5 for 50%).
Enter the probability of Event B the same way.
Click calculate to see the combined probabilities.

Example

If P(A) = 0.5 (a coin landing heads) and P(B) = 0.3 (drawing a red card from a small deck), then P(A and B) = 0.5 × 0.3 = 0.15, and P(A or B) = 0.5 + 0.3 - 0.15 = 0.65.