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Relative Risk Calculator

Relative Risk (RR) compares the probability of an outcome occurring in an exposed group to the probability of the outcome occurring in an unexposed control group.

Exposed participants who developed the outcome.

Exposed participants who did not develop the outcome.

Unexposed control participants who developed the outcome.

Unexposed control participants who did not develop the outcome.

Calculated Result
2.500 RR

Relative Risk

Relative Risk (RR)

2.500

95% Confidence Interval

1.27 – 4.93

Exposed Group Risk

25%

Unexposed Group Risk

10%

Absolute Risk Difference

+15%

Calculation Breakdown

  1. Incidence Risk in Exposed CohortRisk(Exposed) = a ÷ (a + b) = 25 ÷ (25 + 75) = 25%.
  2. Incidence Risk in Unexposed CohortRisk(Unexposed) = c ÷ (c + d) = 10 ÷ (10 + 90) = 10%.
  3. Relative Risk (RR) RatioRR = Risk(Exposed) ÷ Risk(Unexposed) = 25% ÷ 10% = 2.500.

Incidence Comparison by Exposure Group

Interactive visualization based on your current inputs

Risk (%)
0.06.3131925Exposed CohortUnexposed CohortRisk DifferenceCohort GroupIncidence Risk (%)

What Is the Relative Risk Calculator?

A relative risk calculator quantifies the associative strength between an exposure and a subsequent disease or health outcome.

How Does the Relative Risk Calculator Work?

Computes cumulative incidence rates for exposed and control cohorts and determines their ratio and log-transformed confidence interval.

Relative Risk Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

RR = [a ÷ (a + b)] ÷ [c ÷ (c + d)]

Divides incidence risk in the exposed group by incidence risk in the unexposed comparison group.

How to Use the Relative Risk Calculator

  1. Enter the four cells of the 2×2 cohort frequency table.

Step-by-Step Example Calculation

Exposed (25/100) vs Unexposed (10/100)

Input Values:

exposedCases:25
exposedControls:75
unexposedCases:10
unexposedControls:90

Understanding Your Result

RR > 1 indicates increased risk from exposure; RR < 1 indicates protective benefit; RR = 1 indicates no association.

Factors That Affect the Result

  • Confounding variables, cohort attrition, and diagnostic criteria.

When Should You Use This Calculator?

  • Randomized controlled clinical trials, prospective epidemiological studies, and environmental safety assessments.

Assumptions & Limitations

  • Requires prospective follow-up data with known initial denominators.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Standard epidemiological biometric formulas (Rothman & Greenland).

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