# Relative Risk Calculator

> Free relative risk calculator. Get the risk ratio with its 95% confidence interval, absolute and relative risk reduction, p-values, a ready-to-paste AMA sentence and the R script. Your data never leaves your browser.

Canonical: https://biostatkit.com/relative-risk

Enter a 2x2 table from a cohort study or a trial and get the relative risk, the absolute risk reduction (ARR) and the relative risk reduction (RRR), each with a 95% confidence interval, plus a sentence for your manuscript.

## Methods wording

The risk ratio and its 95% CI (Katz log method) and the absolute risk reduction with its 95% CI (Newcombe hybrid score method) were computed with BiostatKit [1].

Method: Katz log CI for RR, Newcombe-Wilson CI for ARR, Pearson chi-square, Fisher exact.

## Frequently asked questions

### What is the difference between relative risk and odds ratio?

The RR compares risks (events divided by group size), the OR compares odds (events divided by non-events). They are close when the outcome is rare. For common outcomes the OR is further from 1 than the RR.

### What is the difference between ARR and RRR?

The ARR is the difference in risk between the groups, in percentage points. The RRR is that difference divided by the risk in the unexposed group. The ARR tells you how many people benefit, the RRR hides the baseline risk.

### What happens with a zero cell?

The RR or its CI cannot be computed from a zero count. This tool adds 0.5 to every cell for the RR and its CI and tells you so; report that choice.

### Is my data stored or sent anywhere?

No. All calculations run in your browser tab. Nothing is uploaded, and the page works offline once loaded.

## Related calculators

- [Odds ratio calculator](https://biostatkit.com/odds-ratio)
- [NNT calculator](https://biostatkit.com/nnt)

Author: TS.BS. Vũ Duy Kiên (https://www.vuduykien.com)