Attributable Risk Calculator
Risk difference and attributable fraction among the exposed.
Enter your values to see the result.
Attributable risk (risk difference) is the excess risk in the exposed group; the attributable fraction is the share of their cases that exposure explains, assuming the association is causal. Confidence intervals use exact (Clopper–Pearson or Poisson) methods. Rates are only comparable between populations with similar age structures unless you standardize them.
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- Population Attributable Risk Calculator — Scale the impact to the whole population.
- Relative Risk Calculator — Get the relative risk with its interval.
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Clear instructions
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How to use the Attributable Risk Calculator
Risk difference and attributable fraction among the exposed.
- 1 Enter cases and totals for exposed and unexposed groups, or the two risks.
- 2 Choose the confidence level.
- 3 Read the attributable risk, attributable fraction and NNH.
Example and practical tips
A risk of 6% in smokers and 2% in non-smokers gives an attributable risk of 4% (40 extra cases per 1,000) and an attributable fraction of 66.7%.
Frequently asked questions
What does the attributable fraction mean?
The share of cases among the exposed that would not occur without the exposure, assuming the link is causal.
How is it different from population attributable risk?
Attributable risk concerns the exposed group only; population attributable risk also accounts for how common the exposure is.
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