How this calculation works
The same risk ratio can correspond to very different absolute risk differences. Report both when the baseline rate matters.
THE FORMULA
RR = (eventsA/totalA)/(eventsB/totalB)A worked example
20 out of 100 versus 10 out of 100 gives a risk ratio of 2.
Good to know
A zero comparison rate makes the ratio undefined.
Reference: OpenStax Introductory Statistics (opens in a new tab) ↗
Read the result
Compare event rates between two groups using a ratio and an absolute difference.
The primary result is labeled “Risk ratio”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
A zero comparison rate makes the ratio undefined.
For a related exercise, try the statistics calculator.
A few questions, answered
How can I check the default inputs by hand?
20 out of 100 versus 10 out of 100 gives a risk ratio of 2.
Which rule does this calculator apply?
RR = (eventsA/totalA)/(eventsB/totalB)