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Relative risk calculator
Relative risk, also called the risk ratio, compares the probability of an outcome in one group with the probability in another group.
Formula
RR = [a/(a+b)] ÷ [c/(c+d)]. A value of 1 indicates equal risk. Values above 1 indicate higher risk in the first group and values below 1 indicate lower risk.
The tool also displays an approximate 95% confidence interval on the logarithmic scale. This calculation is most natural for cohort studies and randomized trials where risks can be directly estimated.
Questions
Frequently asked questions
When should relative risk be used?
Relative risk is commonly used when incidence or risk can be directly measured, such as in cohort studies and randomized trials.