Calculate Incidence Rate

Calculator for the incidence rate from group size and number of cases. The incidence rate tells, how many cases in a group of a certain size, often 100000 (one hundred thousand), occur. In medical terms, these often are newly infected persons per month. Especially during the COVID-19 pandemic , this term found its way from science to everyday language. Incidence is determined through studies; for small groups, new cases are counted and then extrapolated to the reference value.
Reference size is preset to the common value. Please enter two of the three other values, the remaining value will be calculated.

Example: at a group of 2500 people and an incidence rate of 120, 3 affected (ill, infected, ...) people are to be expected.

The word incidence comes from Latin and means event or occurrence. An incidence value essentially indicates how frequently an event occurs. The term incidence value could therefore appear in many areas, but is mostly used in medicine, especially in epidemiology. The corresponding event, which is counted with the incidence value, is a new case of a specific disease. This can be in humans, animals, or possibly even plants. The incidence value is one of several values used to determine the danger of an epidemic. A high incidence value means a large number of new infections. This value says nothing about the severity of the disease, which is of course also an important factor in assessing an epidemic.
The incidence value changes over time, typically increasing slowly at first, then rapidly, then slowly again, although this is of course a gross simplification. External factors, such as weather and measures to fight an epidemic, also affect the incidence value.

Reference size:
Group size:
Number of cases:
Incidence rate: