Probability measures how likely an event is, from 0 (impossible) to 1 (certain). Formula: Probability = Favourable Outcomes / Total Outcomes. Example: rolling a 3 on a die = 1/6 = 0.1667 = 16.67%. Flipping heads on a coin = 1/2 = 0.5 = 50%. Multiple events: P(A and B) = P(A) x P(B) for independent events.
📐 Math
🎲 Probability Calculator
Calculate probability as a fraction, decimal, and percentage. Find probability of single events, multiple events, and complementary events. With clear step-by-step explanations!
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🤔 How Does This Work?
Our Probability Calculator handles four types of probability calculations:
Single event: P(A) = Favourable outcomes / Total outcomes
P(A AND B): For independent events, P(A and B) = P(A) x P(B)
P(A OR B): P(A or B) = P(A) + P(B) - P(A and B) (addition rule)
Complement P(NOT A): P(not A) = 1 - P(A)
All results are shown as fractions, decimals, and percentages with clear explanations.
✅ Trusted Tool
The 365tool.net Probability Calculator uses standard probability theory formulas. Free for students, teachers, data analysts, and anyone studying statistics or chance. Works for independent events — consult a statistics textbook for conditional probability.
❓ FAQ
What is probability in simple words?▼
Probability is a number between 0 and 1 that tells you how likely something is to happen. 0 means impossible. 1 means certain. 0.5 means a 50% chance (like flipping a coin). The higher the number, the more likely the event.
What is the probability of rolling a 6 on a dice?▼
There is 1 way to roll a 6 out of 6 possible outcomes. Probability = 1/6 = 0.1667 = 16.67%. Each number on a fair die has an equal 1/6 = 16.67% chance of appearing on any roll.
How do I calculate the probability of two events both happening?▼
Multiply the individual probabilities together (for independent events). P(A AND B) = P(A) x P(B). Example: probability of flipping heads twice = 0.5 x 0.5 = 0.25 = 25%.
What does complement probability mean?▼
The complement of an event is everything that is NOT that event. P(NOT A) = 1 - P(A). Example: if there is a 30% chance of rain, there is a 70% chance of NO rain (1 - 0.3 = 0.7 = 70%).
What is the probability of winning the lottery?▼
It varies by lottery. A typical 6/49 lottery: probability = 1/13,983,816 = about 0.000007%. You are more likely to be struck by lightning! Probability helps us understand just how rare some events truly are.