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Relative Risk Calculator

Compute relative risk, odds ratio, confidence interval, absolute risk reduction and NNT from a 2×2 table of exposed and unexposed groups.

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Relative Risk Calculator is free to use as often as you like, directly from this page. Its place is under Statistics & probability; ANOVA Calculator (One-Way) and Average Deviation Calculator (mean absolute deviation) answer the questions closest to this one.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Relative Risk Calculator do?

Compute relative risk, odds ratio, confidence interval, absolute risk reduction and NNT from a 2×2 table of exposed and unexposed groups.

When would I actually use this?

Summarising a dataset before drawing conclusions from it, checking whether a difference between two groups is real, and putting an interval around an estimate.

What is the most common mistake?

Reading a p-value as the probability that the hypothesis is wrong. It is the probability of seeing data at least this extreme if the null were true — a different statement, and a much weaker one.

What else is filed next to it?

ANOVA Calculator (One-Way), Average Deviation Calculator (mean absolute deviation) and Bayes Theorem Calculator share its section. They are not variants of it — being filed together is not the same as being alike — but that is where to look if this turned out not to be the tool you wanted.

Where do the figures come from?

Distributions and test statistics are computed from their standard definitions, not from a lookup table, so results carry more digits than a printed table would. The assumptions each test makes are stated with it.

Further reading

All guides →
ExplainerRelative Risk and Absolute Risk Are Not the Same StoryA headline saying 50% higher risk can describe a change of two-tenths of a percentage point. Both numbers come from the same 2x2 table, and computing both takes one line each — here is how, with a worked example, number needed to treat, and where the odds ratio stops approximating relative risk.ExplainerHow Heart Disease Risk Scores Work — and Why They Disagree About YouFramingham, SCORE2 and the pooled cohort equations use overlapping but different inputs and were calibrated on different populations, so the same person gets three different percentages. Here is what each one asks for and what the number means.ExplainerProbability Basics, With ExamplesProbability measures how likely something is, from 0 to 1. Here's the basic idea, how to combine events with AND and OR, and the complement.ExplainerA 1 % Drop Rate Does Not Mean One Hundred RunsAt 1 %, a hundred attempts give you 63.4 % — not certainty. Ninety per cent takes 230 attempts and ninety-nine takes 459, and more than a third of players are still empty-handed at a hundred.ExplainerWhat Is a Z-Score? Standard Deviations Above the MeanA z-score is z = (x − μ) / σ — how many standard deviations a value sits from the mean. Learn how to compute it, read the standard normal curve, and turn it into a percentile.ExplainerMean, Median and Mode: What's the Difference?Mean, median and mode all describe the 'middle' of your data — but answer different questions. Here's what each means, with examples and when to use which.
Relative Risk Calculator — OneKitly