Population Attributable Risk Calculator
Population attributable risk and fraction with Levin's and Miettinen's formulas.
Enter your values to see the result.
The population attributable fraction is the share of all cases that would not occur if the exposure were removed, assuming causation and no confounding. Levin's formula is biased when the RR is confounded; Miettinen's formula with an adjusted RR is preferred.
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- Attributable Risk Calculator — Measure excess risk among the exposed.
- Prevalence Calculator — Estimate the exposure prevalence.
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How to use the Population Attributable Risk Calculator
Population attributable risk and fraction with Levin's and Miettinen's formulas.
- 1 Choose the formula that matches your data.
- 2 Enter exposure prevalence and relative risk, the share of cases exposed, or the two risks.
- 3 Add the total cases to estimate how many could be prevented.
Example and practical tips
With 25% of people exposed and a relative risk of 3, the population attributable fraction is 33.3%.
Frequently asked questions
What does a PAF of 33% mean?
A third of all cases in the population would not occur if the exposure were removed, if the relationship is causal.
Levin or Miettinen?
Levin’s formula is simple but biased by confounding. Miettinen’s formula with an adjusted relative risk gives a valid estimate.
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