Enter the number of cells in mitosis and the total number of cells observed into the calculator to determine the Mitotic Index. This calculator can also evaluate any of the variables given the others are known.

Mitotic Index Formula

The following formula is used to calculate the Mitotic Index.

MI = (M / T) * 100

Variables:

  • MI is the Mitotic Index (%)
  • M is the number of cells in mitosis
  • T is the total number of cells observed

To calculate the Mitotic Index, divide the number of cells in mitosis by the total number of cells observed. Multiply the result by 100 to get the Mitotic Index as a percentage.

What is a Mitotic Index?

A Mitotic Index is a measure used in oncology and other biological sciences to determine the proportion of cells in a tissue sample that are undergoing mitosis. Mitosis is the process of cell division, so a higher mitotic index indicates a higher rate of cell division, which can be a sign of rapid growth or proliferation, such as in a tumor. The index is usually expressed as a percentage and is calculated by dividing the number of cells in mitosis by the total number of cells.

How to Calculate Mitotic Index?

The following steps outline how to calculate the Mitotic Index (MI).


  1. First, determine the number of cells in mitosis (M).
  2. Next, determine the total number of cells observed (T).
  3. Next, use the formula MI = (M / T) * 100 to calculate the Mitotic Index.
  4. Finally, calculate the Mitotic Index.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Number of cells in mitosis (M) = 20

Total number of cells observed (T) = 100