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 Probability CalculatorCalculate binomial probability P(X=k) with the formula C(n,k)·pᵏ·(1−p)^(n−k). Get exact, cumulative probabilities, mean and standard deviation.
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Powerball Odds Calculator (US)Calculate Powerball odds for the jackpot and every prize tier (US rules: 5 of 69 white balls + 1 of 26 red). See your chance per ticket and across multiple lines.
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A/B Test Significance CalculatorCheck if your A/B test result is statistically significant. Enter visitors and conversions for each variant to get Z-score, p-value, uplift, and a verdict.
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Mega Millions Odds CalculatorCalculate your Mega Millions jackpot odds (US lottery). Uses 1 / (C(70,5)×25) = 1 in 302,575,350 with a configurable ball matrix.
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Standard Error of a Proportion CalculatorCalculate the standard error of a sample proportion using SE = sqrt(p(1-p)/n). Enter your proportion and sample size for instant, accurate results.
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D&D Advantage / Disadvantage Dice CalculatorCalculate your chance to hit a d20 target number with Advantage, Disadvantage, or a normal roll in Dungeons & Dragons 5e.
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Lottery Expected Value CalculatorCalculate the expected value of a lottery ticket from the jackpot, odds, and ticket price. See if a ticket is worth it in the long run.
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Exact Binomial Test CalculatorCompute the exact binomial test p-value (two-sided and one-sided) for k successes in n trials against a hypothesized probability p.
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Confidence Interval for Difference of Two ProportionsCompute a confidence interval for the difference between two sample proportions (p̂₁−p̂₂) at 90%, 95%, or 99% using the normal approximation.
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Law of Total Probability CalculatorCompute P(A) from conditional and partition probabilities using the law of total probability: P(A) = Σ P(A|Bᵢ)·P(Bᵢ). Supports up to 3 events.
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Confidence Interval for Difference of Two Means CalculatorCompute a confidence interval for the difference between two independent sample means using the Welch t-method. Enter means, SDs, sizes and confidence level.
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Sample Size from Margin of Error CalculatorCalculate the survey sample size needed for a target margin of error and confidence level using n = z² p(1−p)/E², with optional finite population correction.
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Shannon Entropy CalculatorCompute Shannon entropy H = -Σ pᵢ·log₂(pᵢ) from a probability distribution. Supports bits, nats and dits, plus max entropy and efficiency.
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Cohen's Kappa CalculatorCalculate Cohen Kappa (κ) for inter-rater agreement from a 2x2 table. Get observed and expected agreement and interpret reliability instantly.
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Sample Variance CalculatorCalculate sample variance (s²) and standard deviation from a data set. Uses the n−1 unbiased formula, with mean and sum of squared deviations.
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Probability of Rolling a Specific Sum CalculatorFind the exact probability of rolling a chosen sum with any number of dice and sides. Uses convolution counting: P = (ways to make sum) / sides^n.
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Probability X Greater Than a Value (Normal Distribution)Compute P(X > x) for a normal distribution from mean, standard deviation, and a value. Returns the right-tail probability, z-score, and percentage.
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Cumulative Binomial Probability CalculatorCompute cumulative binomial probability P(X≤k) for n trials with success probability p. Also returns P(X=k), P(X>k), P(X≥k) and the mean.
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Parlay Odds CalculatorCalculate parlay payout and combined decimal odds for multi-leg bets. Enter your stake and up to 6 legs to see total payout and profit instantly.
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Fisher's Exact Test Calculator (2x2)Compute the exact p-value for a 2x2 contingency table using Fisher exact test. Get the hypergeometric probability and two-sided p-value instantly.
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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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Mean Absolute Deviation (MAD) CalculatorCalculate the Mean Absolute Deviation (MAD) of any data set instantly. Enter your numbers to find the average distance from the mean, plus the mean and count.
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Hypergeometric Probability CalculatorCompute hypergeometric probabilities P(X=k), cumulative P(X≤k) and P(X≥k), plus mean and variance for sampling without replacement.
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Normal Probability Between Two X Values CalculatorFind P(a<X<b) for a normal distribution. Enter the mean, standard deviation and two X values to get the probability and z-scores instantly.
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.
