Probability Calculator

Calculate basic, complementary, union, and intersection probabilities. Use this free browser-based probability calculator from XTRAW Tools.

Probability Calculator helps you calculate basic, complementary, union, and intersection probabilities. Use this free browser-based calculator from XTRAW Tools to compare inputs, estimate results, and plan your next step.

How to Use the Probability Calculator

Enter the required calculator inputs shown in the form.
Review the probability, experiment, sample, velocity, acceleration, distance, force, angle, or physics assumptions.
Run the calculator, then adjust one input at a time to compare scenarios or check your estimate.

What This Calculator Helps With

Calculate basic, complementary, union, and intersection probabilities. It is designed for students, teachers, probability learners, analysts, game users, researchers, and anyone working with probability or counting problems who want a fast, browser-based estimate before relying on a spreadsheet, textbook, analytics platform, physics software, research software, professional source, or specialist.

P(A): 0.4
P(B): 0.3
Events are: independent

Common Uses

People use this calculator when they need a quick way to estimate chance, count outcomes, compare probability assumptions, or check a combinatorics formula.

Math Solving: Solve probability, combinatorics, A/B testing, effect size, physics, motion, force, or work formulas from entered values.
Random Selection: Explore lottery, probability, and counting outcomes for education, planning, and chance demonstrations.
Measurement: Measure odds, combinations, conversion lift, effect size, velocity, acceleration, force, work, range, or related computed values.

Formula or Method

P(A∪B) = P(A) + P(B) − P(A∩B); P(A∩B) = P(A)×P(B) if independent

Example

Example inputs: P(A): 0.4; P(B): 0.3; Events are: independent

Example result: Using independent default events, P(A∩B) is 0.12 and P(A∪B) is 0.58.

Related Tools

Probability Calculator FAQ

Is the Probability Calculator free?

Yes. This calculator is free to use on XTRAW Tools.

Do I need to create an account?

No. XTRAW tools are designed for browser-based use without requiring an account.

Are the results exact?

Results may be estimates depending on the inputs, formula, rounding, selected method, probability model, physics assumption, or purpose of the calculator. Always verify important results before relying on them.

Disclaimer: This calculator is provided for general informational, educational, and convenience purposes only. It is not legal, financial, medical, gambling, lottery, academic, research, statistical consulting, safety, or professional advice. Always verify important results with a qualified professional, instructor, statistician, researcher, lottery authority, authoritative source, or appropriate specialist before making decisions.