Odds ratio with confidence interval, z-test and Fisher's exact p from a 2×2 table.
How to use Odds Ratio Calculator
Enter exposed and unexposed counts for cases and controls.
Pick the confidence level.
Read the odds ratio, its confidence interval and the p-values.
Worked example
With 40 exposed and 20 unexposed cases against 60 exposed and 80 unexposed controls, the odds ratio is 2.67 (95% CI 1.42 to 5.02).
When should I use an odds ratio instead of relative risk?
Use the odds ratio for case-control studies, where you choose people by outcome and cannot measure risk directly. It also comes out of logistic regression.
What if a cell is zero?
The odds ratio would be zero or infinite, so 0.5 is added to every cell (the Haldane–Anscombe correction) and a note is shown.
Put this guide into practice
Odds Ratio Calculator — Odds ratio with confidence interval, z-test and Fisher's exact p from a 2×2 table.