Ovulation Calculator — Ovulation Date & Fertile Window
Free ovulation calculator. Find your estimated ovulation date, fertile window, and next period date based on your last menstrual period and cycle length.
Calculate your estimated ovulation date and fertile window based on the first day of your last menstrual period (LMP) and your average cycle length. The fertile window is the 6-day period when conception is most likely.
Formula: Ovulation = LMP + (cycle length − 14 days)
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Typical range: 21–45 days. Default is 28.