Relative Risk Calculator
Compare the risk of an outcome between an exposed and unexposed group. Enter the four counts from your 2x2 table.
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Relative risk vs odds ratio
Relative risk is the probability of the outcome in the exposed group divided by the probability in the unexposed group. A value of 1 means no difference, above 1 means higher risk with exposure and below 1 means lower risk. It is more intuitive than the odds ratio, which compares odds rather than probabilities, though the two agree closely when the outcome is rare.
How the counts map
Enter exposed-with-outcome, exposed-without-outcome, unexposed-with-outcome and unexposed-without-outcome. If any cell is zero, a Haldane-Anscombe correction of 0.5 is added to every cell so the ratio and its confidence interval stay defined. A 95% interval that excludes 1 points to a statistically significant association.
Frequently asked questions
Should I report relative risk or the odds ratio?
For cohort and experimental data where you can measure risk directly, relative risk is usually the clearer choice. Case-control studies typically report the odds ratio instead.
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