Odds Ratio Calculator
Enter four nonnegative integer counts to calculate OR = ad/(bc).
OR = (a × d) ÷ (b × c).
OR is an association measure, not causation. OR is not RR and does not directly calculate risk; it may approximate RR for rare outcomes.
A QUICK WALKTHROUGH
How to use this tool
- Enter all four counts.
- Calculate the odds ratio.
- Review the undefined denominator and interpretation limits.
Formula
OR = ad/(bc) for a 2×2 table.
Interpretation
An odds ratio is an association measure, not causation. OR is not RR and does not directly calculate risk; it can approximate RR when the outcome is rare.
Local processing
Inputs and arithmetic stay in this browser.
GOOD TO KNOW
Common questions
What if bc is zero?
The odds ratio is explicitly undefined; this tool applies no continuity correction.
Is OR the same as RR?
No. Odds ratio is not relative risk and does not directly calculate risk.