How to use the relative risk and odds ratio calculator
Compute risk ratio and odds ratio from exposure outcomes. Enter exposed with outcome, exposed without outcome, unexposed with outcome, unexposed without outcome in the fields above; the risk (exposed), risk (unexposed), relative risk, odds ratio, absolute risk reduction are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- a — Exposed with outcome
- b — Exposed without outcome
- c — Unexposed with outcome
- d — Unexposed without outcome
Worked example
With exposed with outcome = 30, exposed without outcome = 70, unexposed with outcome = 10, unexposed without outcome = 90, the calculator gives risk (exposed) ≈ 0.3; risk (unexposed) ≈ 0.1; relative risk ≈ 3; odds ratio ≈ 3.857143; absolute risk reduction ≈ 0.2.
Frequently asked questions
What is the formula for the relative risk and odds ratio calculation?
Risk (exposed) = a / (a+b). Risk (unexposed) = c / (c+d). Relative risk = [Risk (exposed)] / [Risk (unexposed)]. Odds ratio = (a × d) / (b × c). Absolute risk reduction = [Risk (exposed)]-[Risk (unexposed)]. Here a is exposed with outcome, b is exposed without outcome, c is unexposed with outcome, d is unexposed without outcome.
What inputs do I need for the relative risk and odds ratio calculator?
You need exposed with outcome, exposed without outcome, unexposed with outcome, unexposed without outcome. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.