These calculators handle probability, statistics, and decision analysis. The Z Score Calculator and Probability Between Two Z-Scores Calculator cover standard-normal problems, the Quartile Calculator summarizes distributions, and the Permutation with Replacement Calculator handles counting problems quickly. More advanced tools like the Expected Return Calculator, Expected Utility Calculator, and Incomplete Beta Function Calculator serve statistical modeling and quantitative analysis.
Browse the most-popular list to see which tools students and analysts reach for most, or open the Trending tab for what's gaining traction. Every calculator is free, requires no account, and works on any device.
- Fraction Calculator
- Matrix Calculator
- Slope Calculator
- Algebra Calculator
- Trigonometry Calculator
- Percentage Calculator
- Probability Calculator
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Binomial Confidence Interval CalculatorCompute a Wilson score confidence interval for a binomial proportion. Enter successes, trials and a confidence level to get the lower and upper bounds.
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Possible Combinations CalculatorCalculate the number of possible combinations C(n,r) = n!/(r!(n-r)!). Find how many ways to choose r items from n, plus permutations P(n,r).
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Random Number Generator (1 to 100)Free random number generator from 1 to 100. Click Pick for a uniform random integer (each number 1% likely), with a running pick counter and Reset.
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Bingo Number GeneratorFree online Bingo caller and number generator. Draw random balls without replacement from 1-75 or 1-90, with B-I-N-G-O letters and a live call board.
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Custom Dice Roller CalculatorRoll any number of custom-sided dice (NdS) with an optional modifier. Get a live random total plus the minimum, maximum, and average outcome.
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Independent Events Probability CalculatorCalculate the probability of two independent events: P(A and B), P(A or B) and P(neither) using the multiplication and addition rules. Free and instant.
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Sample Size Calculator for a MeanCalculate the required sample size to estimate a population mean within a target margin of error and confidence level using n = (z·σ/E)².
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Geometric Distribution CalculatorCompute geometric distribution PMF, lower and upper cumulative probability, and mean for x failures before the first success with success probability p.
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Kelly Criterion CalculatorCalculate the optimal bet or investment fraction with the Kelly Criterion. Enter win probability and odds to get your ideal stake and half-Kelly amount.
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Probability CalculatorFree probability calculator for two independent events. Compute P(A and B), P(A or B), P(neither) and P(not both) instantly from decimal inputs.
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Z-Score to Probability CalculatorConvert a z-score to a probability using the standard normal CDF. Get left-tail, right-tail, and two-tailed p-values from any z value instantly.
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99% Confidence Interval CalculatorCalculate a 99% confidence interval from your sample mean, standard deviation, and sample size using the z-score 2.576. Free and instant.
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Studentized Range Distribution Probability CalculatorCompute the lower and upper cumulative probability of the studentized range distribution (Tukey q statistic) for a quantile q, sample size r, df nu and c groups.
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Absolute Value Graph Vertex CalculatorFree combination (nCr) calculator. Find how many ways to choose r items from n where order does not matter, using C(n,r) = n!/(r!(n-r)!).
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Negative Binomial Mean and Variance CalculatorCalculate the interquartile range (IQR = Q3 − Q1) from your data set. Get Q1, median, Q3, IQR and outlier fences instantly with this free IQR calculator.
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Chi-Squared Distribution Graph CalculatorCompute the chi-squared (chi^2) probability density f, lower cumulative P, and upper cumulative Q for any x and degrees of freedom, plus a series for graphing.
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Gaussian Percentile Rank & Upper-Tail Probability CalculatorCompute P(Z > z) = 1 − Φ(z), the upper-tail probability of the standard normal distribution, plus the cumulative probability and percentile rank for any z-score.
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Z Score CalculatorCalculate the z score (standard score) of a value from the mean and standard deviation using z = (x − μ) / σ. Free, instant, and accurate.
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Gamma Function CalculatorCompute the Gamma function Γ(z) for any real number using the Lanczos approximation. Handles negative non-integer values via the reflection formula.
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Normal Distribution Percentile Point CalculatorFind the percentile point (quantile) of a normal distribution from a lower- or upper-tail cumulative probability. Inverse normal CDF with custom mean and standard deviation.
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Confidence Interval for a Mean CalculatorCompute a confidence interval for a population mean using the Student-t distribution. Enter sample mean, standard deviation, size, and confidence level.
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Binomial Probability Calculator P(X=k)Calculate the exact binomial probability P(X=k) for n trials with success probability p. Free online tool using the binomial formula with worked examples.
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Z-Score to Percentile Rank CalculatorConvert a z-score to a percentile rank using the standard normal distribution. Enter any z value to find the percentage of data below it.
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Softmax Function CalculatorCompute the softmax of an input vector online. Converts any list of real numbers into a probability distribution that sums to 1. Numerically stable.
Frequently asked questions
What kinds of probability problems can I solve here?
You can calculate z-scores and the probability that a value falls between two z-scores, find quartiles to summarize a distribution, count permutations with replacement, convert between odds and probability, estimate expected returns and expected utility, and evaluate the incomplete beta function — spanning introductory statistics through quantitative modeling.
How accurate are the statistical results?
All tools implement standard mathematical formulas and numerical methods — for example, the normal cumulative distribution function for z-score probabilities. Results are mathematically precise for the inputs you provide. For high-stakes academic, research, or financial work, double-check key outputs against a verified statistical reference or authoritative source.
Are these calculators suitable for coursework or professional use?
Yes, for learning, exploration, and quick verification. They are well suited for checking hand calculations or working through concepts. For peer-reviewed research or professional analysis, confirm results using dedicated statistical software and apply the methodological standards required by your field.
Do you store the values I enter?
No. Every calculation runs locally in your browser. No inputs — sample sizes, probabilities, distribution parameters, or anything else — are transmitted to our servers or retained between sessions.
Which probability calculators are most popular?
The list is ranked by real visitor usage, so the top entries reflect what students and professionals find most useful. Open the Trending tab to see which tools are currently getting the biggest surge in traffic.
