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Interactive Tool: When Are You Most Fertile?

What does this tool help you learn?

This tool estimates your peak fertility period, also known as your "fertile window." This is when you are most likely to get pregnant. Do not use this tool to prevent pregnancy.

In the tool, you will enter the typical length of your menstrual cycle, Opens dialog, and you will click on the first day of your last menstrual period.

  • To know how long your cycles are, track the number of days on a calendar for 2 or 3 months or cycles. Your menstrual cycle begins with the day your period starts and ends the day before your next period starts.
  • If you don't know the number of days in your menstrual cycle, you can use 28 days. This is the average length of a menstrual cycle. But if your cycle is longer or shorter than that, or if it isn't always the same length, this tool will not predict your fertile window very well.

Fritz MA, Speroff L (2011). "Clinical Gynecologic Endocrinology and Infertility," 8th ed., Philadelphia: Lippincott Williams and Wilkins.

Peak Fertility
Menstrual cycle:
(If unknown, enter 28 days.)
Select the first day of your last menstrual period.


Your best chance to get pregnant is
itools-10.7.10.1

Current as of: April 30, 2024

Author: Ignite Healthwise, LLC Staff

Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.