Ovulation Calculator

Find your likely ovulation day and fertile window using the first day of your last period and your typical cycle length.

Results

Estimated ovulation day

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Fertile window

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Next period estimate

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Cycle day today

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How this calculator works

This calculator estimates ovulation timing from your last menstrual period (LMP) and typical cycle length. It assumes ovulation occurs about 14 days before your next period, which can vary by person and cycle.

Enter your LMP date and usual cycle length; leave cycle length blank to use 28 days.
We estimate ovulation by counting backward ~14 days from your next predicted period and show a fertile window around that day.
Cycles vary and ovulation can shift; use this as a guide only and consult your clinician for medical advice.