Probability Calculator
Calculate probability for single events, complementary events (not A), union P(A or B), and intersection P(A and B) for independent events. Free and instant.
Probability Calculator
toolznova.com • Free Calculator
How to Use
Calculate probability in 3 steps.
Choose Type
Select single event, complement, union, or intersection.
Enter Values
Enter favorable/total outcomes or probability values.
Get Probability
Click Calculate for probability as decimal and percentage.
Why ToolzNova?
Instant
Results in milliseconds.
Accurate
Precise formulas every time.
Private
No data sent anywhere.
Everywhere
Mobile, tablet, desktop.
Why Calculate Probability?
- Statistics: Foundation of all statistical inference and hypothesis testing.
- Risk Assessment: Probability of events for insurance and risk management.
- Games: Understand winning probability in games and lotteries.
- Finance: Option pricing and financial risk models use probability.
- Science: Quantum mechanics and experimental science use probability.
- Decision Making: Make informed decisions under uncertainty.
Tips & Examples
- Probability always ranges from 0 (impossible) to 1 (certain).
- P(A or B) = P(A) + P(B) − P(A and B) — subtract overlap.
- P(A and B) = P(A)×P(B) only for independent events.
- Complement: P(not A) = 1 − P(A) — always true.
- Coin flip: favorable=1, total=2. P(heads)=0.5=50%.
- Dice roll: P(6) = 1/6 ≈ 16.7%.
Free Probability Calculator Online
ToolzNova's free probability calculator computes single event probability, complement probability, union P(A or B), and intersection P(A and B) for independent events — with percentage results.
Probability quantifies how likely events are to occur on a scale from 0 to 1. Understanding probability is essential in statistics, science, finance, and everyday decision-making.
Probability Formulas
Single: P(A) = Favorable/Total. Complement: P(A') = 1−P(A). Union: P(A∪B) = P(A)+P(B)−P(A∩B). Intersection (independent): P(A∩B) = P(A)×P(B).