Mitotic Index Calculator

The Mitotic Index measures the proportion of cells actively dividing in a tissue sample — a key indicator used in biology and pathology to assess cell growth rates and tumor aggressiveness. Enter the number of cells in mitosis and the total number of cells observed to get the Mitotic Index as a percentage and mitotic fraction. Optionally, break down your count by phase — prophase, metaphase, anaphase, and telophase — to see the percentage distribution across each stage of cell division.

Count all cells showing signs of mitosis (prophase, metaphase, anaphase, telophase)

Total number of cells counted in your sample

Cells in prophase stage (optional for detailed analysis)

Cells in metaphase stage

Cells in anaphase stage

Cells in telophase stage

Results

Mitotic Index

--

Mitotic Fraction

--

Prophase Percentage

--

Metaphase Percentage

--

Anaphase Percentage

--

Telophase Percentage

--

More Biology Tools

Frequently Asked Questions

What is a Mitotic Index?

The mitotic index is a measure of cellular proliferation that represents the fraction or percentage of cells in a tissue sample that are actively dividing (undergoing mitosis). It's calculated by dividing the number of cells in mitosis by the total number of cells observed and multiplying by 100.

How do you calculate the Mitotic Index?

The mitotic index is calculated using the formula: MI = (M / T) × 100, where M is the number of cells in mitosis and T is the total number of cells observed. The result gives you the percentage of cells actively dividing.

What is considered a normal Mitotic Index?

Normal mitotic index values vary by tissue type and organism. In humans, typical values range from 0.5% to 3% for most tissues, though rapidly dividing tissues like bone marrow or intestinal epithelium can have higher values. Cancer tissues often show elevated mitotic indices.

Which phases of mitosis should I count?

Count all cells showing clear signs of mitosis: prophase (condensed chromosomes), metaphase (chromosomes aligned at the equator), anaphase (chromosomes separating), and telophase (nuclear division completing). Do not count interphase cells.

How many cells should I count for accurate results?

For reliable results, count at least 500-1000 cells total. Larger sample sizes provide more accurate mitotic index calculations and reduce sampling error. The exact number depends on your research requirements and the mitotic activity of your tissue.

What factors can affect the Mitotic Index?

Several factors influence mitotic index including tissue type, age of organism, time of day (circadian rhythms), growth conditions, disease states, and drug treatments. Cancer tissues typically show higher mitotic indices than normal tissues.

Can I use this calculator for different species?

Yes, the mitotic index calculation formula is universal across species since it's simply a ratio of dividing cells to total cells. However, normal reference values vary significantly between different organisms and tissue types.

What's the difference between mitotic index and proliferation rate?

Mitotic index is a snapshot measurement of cells in mitosis at a specific time, while proliferation rate considers the duration of cell division. Mitotic index provides an estimate of proliferative activity but doesn't account for cell cycle length variations.