Probability Calculator
Calculate the probability of single events and combined events (and/or). Enter counts or fractions to find probability, odds, and complementary probability in one step.
P(A and B)
0.2000
P(A or B)
0.7000
P(only A)
0.3000
P(¬A)
0.5000
P(¬B)
0.6000
P(neither)
0.3000
How to use the probability calculator
Enter the probabilities of two independent events as decimals between 0 and 1.
Formula & explanation
Independent events: P(A∩B) = P(A)·P(B). P(A∪B) = P(A)+P(B)−P(A∩B). P(¬A) = 1−P(A).
Examples
P(A)=0.5, P(B)=0.4 → P(both) = 0.20, P(either) = 0.70, P(neither) = 0.30.
Frequently asked questions
- What if A and B are dependent?
- These formulas assume independence. For dependent events you need conditional probabilities.
Related math tools
- Scientific CalculatorFull scientific calculator with trigonometric functions (sin, cos, tan), logarithms, exponents, factorials, and constants. Supports degree and radian mode.
- Average CalculatorCalculate mean, median, mode, range, sum, min, and max for any list of numbers. Paste in grades, scores, or measurements — results update instantly.
- Ratio CalculatorSimplify ratios to lowest terms, convert a ratio to a decimal, scale to any value, and compare two ratios. For recipes, map scales, and aspect ratios.
- Root CalculatorCalculate square roots, cube roots, and any nth root with high precision. Handles perfect squares and irrational results — shows the decimal approximation and the radical form.
- Permutation & Combination CalculatorCalculate nPr (permutations) and nCr (combinations) with a step-by-step formula breakdown. Enter n and r to see the count, formula expansion, and intermediate values.
- Percentage CalculatorCalculate what percent of a number is, find percent change, and reverse-calculate any percentage. Three modes — pick the one that matches your problem, get the answer instantly.