Odds Ratio Calculator
2×2 table to odds ratio with a confidence interval.
Enter your values
Enter the exposed with the outcome you are working with.
Enter the exposed without you are working with.
Enter the unexposed with the outcome you are working with.
Enter the unexposed without you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Odds ratio
- 2.6667
- 95% confidence interval
- 1.417 to 5.02
- Significant?
- Yes — the interval excludes 1
- Log odds ratio
- 0.9808
- Odds in the exposed group
- 0.6667
- Odds in the unexposed group
- 0.25
Quick answer
The odds ratio is (a·d) ÷ (b·c) from a 2×2 table; a value of 1 means no association, above 1 means higher odds in the exposed group.
OR = (a·d) ÷ (b·c)
At a glance
| What it does | 2×2 table to odds ratio with a confidence interval. |
|---|---|
| Category | Statistics |
| Inputs needed | Exposed with the outcome, Exposed without, Unexposed with the outcome, Unexposed without |
| Main output | Odds ratio |
| Formula | OR = (a·d) ÷ (b·c) |
| Cost | Free — no sign-up, no download |
How to use the Odds Ratio Calculator
- 1Fill in the four cells of your 2×2 table.
- 2Read the odds ratio and its confidence interval.
- 3If the interval crosses 1, the association is not statistically significant.
Inputs explained
- Exposed with the outcome
- Enter the exposed with the outcome you are working with.
- Exposed without
- Enter the exposed without you are working with.
- Unexposed with the outcome
- Enter the unexposed with the outcome you are working with.
- Unexposed without
- Enter the unexposed without you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- Exposed with the outcome40
- Exposed without60
- Unexposed with the outcome20
- Unexposed without80
Results
- Odds ratio2.6667
- 95% confidence interval1.417 to 5.02
- Significant?Yes — the interval excludes 1
- Log odds ratio0.9808
- Odds in the exposed group0.6667
- Odds in the unexposed group0.25
Frequently asked questions
Odds ratio or relative risk?
Use relative risk for cohort studies where you can measure risk directly. Odds ratios are the only option in case-control designs.
What if a cell is zero?
The formula breaks. Add 0.5 to every cell (the Haldane correction) or use exact methods.
What do I need to enter into the Odds Ratio Calculator?
Just 4 values: exposed with the outcome, exposed without, unexposed with the outcome, unexposed without. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Odds Ratio Calculator work out the answer?
The odds ratio is (a·d) ÷ (b·c) from a 2×2 table; a value of 1 means no association, above 1 means higher odds in the exposed group. It applies the formula OR = (a·d) ÷ (b·c) and shows the working so you can check each step by hand.
Is the Odds Ratio Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.