Person-Time Incidence Rate Calculator
Incidence rate per person-years with an exact Poisson 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
- Incidence Calculator — Calculate cumulative incidence.
- Mortality Rate Calculator — Calculate death rates.
Share this tool
Found it useful? Send it to a friend or teammate.
Rate this tool
0.0
0 ratings
- 5 stars 0
- 4 stars 0
- 3 stars 0
- 2 stars 0
- 1 star 0
Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
No sign-up required. Tool-specific limits may apply.
How to use the Person-Time Incidence Rate Calculator
Incidence rate per person-years with an exact Poisson interval.
- 1 Enter the number of new cases.
- 2 Enter the total person-time at risk and its unit.
- 3 Choose the multiplier and read the rate with its interval.
Example and practical tips
28 cases over 12,500 person-years is an incidence rate of 2.24 per 1,000 person-years (95% CI 1.49 to 3.24).
Frequently asked questions
When should I use person-time?
When people are followed for different lengths of time, as in most cohort studies, so each person contributes only their time at risk.
How is the confidence interval calculated?
With the exact Poisson method based on the chi-square distribution, which works even for small case counts.
Report an issue
Something broken or not quite right? Tell us and we will look into it.