Statistics calculators
Probability, confidence, and sample-size tools.
- Probability to Odds Converter (Odds For, Odds Against, 1 in N)
Probability to odds and back — odds in favour, odds against, fractional and decimal forms, and '1 in N'.
- Z-Score Calculator (Standard Score and Percentile)
How many standard deviations a value is from the mean, with the percentile it corresponds to on a normal curve.
- Confidence Interval Calculator for a Mean (z, Known σ)
A 90%, 95% or 99% confidence interval for a population mean from a sample mean, standard deviation and sample size, working shown.
- Sample Size Calculator for a Mean (Margin of Error and Confidence)
How many observations you need to estimate a mean within a chosen margin of error at 90%, 95% or 99% confidence.
- Pearson Correlation Coefficient Calculator (r, R² and the Regression Line)
Pearson's r for any number of (x, y) pairs, with the sums it is built from, R² and the least-squares line.
- Normal Distribution Calculator (Z-Table, CDF and Two-Tailed Probability)
The probability below, above, between and beyond a z-score on the standard normal curve — a z-table without the table.
- Margin of Error Calculator (Mean, z-Interval)
The margin of error for a sample mean from the standard deviation, sample size and confidence level, working shown.
- Standard Error of the Mean Calculator (σ ÷ √n)
The standard error of a sample mean from the standard deviation and sample size, with the 95% error bound and how n changes it.