Incidence Calculator
Cumulative incidence (risk) with an exact confidence interval.
Enter your values to see the result.
Confidence intervals use exact (Clopper–Pearson or Poisson) methods. Rates are only comparable between populations with similar age structures unless you standardize them.
Continue your work
- Person-Time Incidence Rate Calculator — Use person-time when follow-up varies.
- Prevalence Calculator — Calculate prevalence.
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Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
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How to use the Incidence Calculator
Cumulative incidence (risk) with an exact confidence interval.
- 1 Enter the number of new cases during the period.
- 2 Enter the population at risk at the start.
- 3 Choose the multiplier and read the incidence with its interval.
Example and practical tips
45 new cases among 3,000 people at risk is a cumulative incidence of 15 per 1,000 (95% CI 10.96 to 20.02).
Frequently asked questions
What is the difference between incidence and prevalence?
Incidence counts new cases over a period; prevalence counts everyone who has the condition at a point in time.
Who is “at risk”?
People who could develop the condition during the period, so exclude those who already have it or cannot get it.
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