Statistics
Averages, spread, probability and rate calculations.
Tools for summarising data and working with likelihood — averages and spread, probability, and the rate calculations that come up in reporting.
The arithmetic is straightforward. Most of the difficulty in statistics is deciding which measure answers your question, which is what the notes below are about.
4 calculators in this category
Statistics Calculator
Calculate mean, median, mode, standard deviation, and variance.
Percentage Change Calculator
Calculate percentage increase, decrease, or difference between values.
Probability Calculator
Calculate basic probability, combinations, and permutations.
Engagement Rate Calculator
Calculate social media engagement rate for Instagram, TikTok, YouTube, and Twitter.
Which calculator do I need?
Start from the job rather than the tool.
- Summarise a dataset — Statistics Calculator
- Work out how much something changed — Percentage Change Calculator
- Calculate the likelihood of an event — Probability Calculator
- Measure social media engagement — Engagement Rate Calculator
What these calculators have in common
Assumptions worth knowing before you rely on any result here.
The mean is not always the right average
One extreme value drags the mean a long way. Incomes, house prices and response times are usually better described by the median, which ignores how far out the outliers sit.
Percent and percentage points are different
A rate moving from 4% to 6% is a rise of 2 percentage points and also a 50% increase. Both are correct, and saying which you mean prevents a genuinely misleading claim.
Small samples produce unstable numbers
A mean from five values can swing wildly with one more observation, and standard deviation is especially unreliable below about ten. Treat statistics from tiny samples as an indication rather than a finding.