# Odds Ratio Calculator

Instructions: This calculator computes the Odds Ratio (OR) for a 2×2 crosstabulation, which measures the ratio of the odds of exhibiting a condition (or disease) for those in an exposed group, versus the the odds of exhibiting the condition (or disease) for those in the non-exposed group. Please type the 2×2 table data and also indicate the confidence level required to compute the confidence interval for the odds ratio (OR)

Disease
No Disease
Exposed
Not Exposed
Confidence Level =

#### How Do You Calculate Odds Ratios?

More about the Odds Ratio (OR)

The odds ratio (OR) corresponds to ratio of the odds of having a condition for those exposed to a certain treatment, versus the the odds of having a condition for those not exposed to the treatment.

Let us consider the folllowing 2×2 crosstabulation:

Disease
No Disease
Exposed
$$a$$
$$b$$
Not Exposed
$$c$$
$$d$$

The Odds Ratio of having the condition for those in the exposed group respect to the non-exposed group is computed using the following formula:

$OR = \frac{a/b}{c/d}$