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Menstrual Cycle Length Stats Study


How long is the typical/average menstrual cycle?

We analyzed the duration of menstrual cycles of roughly 21,000 fertility/ovulation charts on

This statistical study measured the length of each cycle from the first day of bleeding (included) to the start of the next bleeding (excluded).


Statistical Summary

The descriptive stats for this sample are:

Sample Size:21680 Charts.
Average:30.38 Days.
Median:29 Days.
Standard Deviation:5.62.

Mythical 28 Days Cycle?

We found that 11.28% of the sample's charts had a cycle length of exactly 28 days and 16% had a cycle length of 35 days or more.

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