Details

First day of last period

Average cycle length (days)

Luteal phase (days)

Result

Estimated ovulation

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Fertile window start—

Fertile window end—

Next period expected—

Cycle day today—

Ovulation typically occurs 14 days before the next period (not 14 days after the last period). The fertile window spans 5 days before ovulation to 1 day after, as sperm can survive up to 5 days. This calculator provides estimates only — actual ovulation varies with stress, illness, and cycle irregularity.

Ovulation Calculator