Odds Ratio Calculator
Compare event odds between exposed and control groups.
How the odds ratio calculator works
An odds ratio compares event odds across two groups in a two-by-two table. Odds are event count divided by non-event count, not event probability. Dividing exposed odds by control odds is algebraically the same as the diagonal cross-product a times d divided by b times c. This calculator reports both group odds and their ratio so direction is explicit.
The defaults use exposed counts 40 events and 10 non-events, giving odds 4. Control counts 20 events and 30 non-events give odds two thirds. Dividing 4 by two thirds produces the verified odds ratio 6. The cross-product check gives 40 times 30 divided by 10 times 20, also 6.
Reading odds ratio calculator results privately
An odds ratio is not a risk ratio, especially when events are common. Zero cells create zero or infinite raw odds and require a continuity correction or exact method not silently applied here. Association does not establish causality, and uncertainty requires a confidence interval. Group and event labels determine whether the ratio or its reciprocal is reported. This odds ratio calculator calculation runs entirely in your browser, so the numbers you enter never leave your device.
Frequently Asked Questions
Is an odds ratio the same as relative risk?
No. Odds divide events by non-events, while risk divides events by all group members. They are close only for rare events.
What does an odds ratio of one mean?
The event odds are equal in the two groups under the entered orientation.
Is the odds ratio calculator private?
Yes. Its inputs and results stay in your browser. Bushe.co does not upload or store the values used in this calculation.
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