TimelyScholarFree Tools › Odds Ratio Calculator
Enter a 2×2 table to calculate the odds ratio, its confidence interval and p-value. Zero cells are handled automatically.
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| Event | No event | |
|---|---|---|
| Exposed / treatment | ||
| Unexposed / control |
| Odds ratio (OR) | 2.250 |
|---|---|
| 95% CI | 0.994 to 5.092 |
| z statistic | 1.946 |
| p-value (two-sided) | 0.052 |
| SE of ln(OR) | 0.4167 |
The odds of the event are 2.25 times as high in the first group (95% CI 0.99 to 5.09). The confidence interval includes 1, so the data are compatible with no difference in odds.
Events and non-events for each group.
90%, 95% or 99%.
Use the APA-style sentence in your results section.
The odds ratio compares the odds of an event in one group with the odds in another. An odds ratio of 1 means no difference; above 1 means higher odds in the first group; below 1 means lower odds.
Odds ratios are the standard effect measure for case-control studies and logistic regression, and are widely used in meta-analyses of binary outcomes.
No. They are similar when the outcome is rare, but the odds ratio moves further from 1 than the risk ratio when outcomes are common. Use our relative risk calculator for risks.
The data are compatible with no difference in odds at your chosen confidence level.
When any cell is zero, 0.5 is added to all four cells so the odds ratio and its interval can be estimated.