Ovulation Window
Estimate ovulation, fertile days, peak timing and next period from your cycle pattern
Calculate to see your ovulation window
Key dates appear here
Metrics appear after calculation
Your explanation appears here
Cycle-based ovulation dates can shift. Cervical mucus, LH tests and clinician guidance can improve timing accuracy.
Your plan appears after calculation
Compare how a longer or shorter cycle changes the predicted ovulation window.
Calculate your baseline first
It treats the first day of your last period as cycle day 1, predicts the next period from your average cycle length, then estimates ovulation by subtracting the luteal phase estimate from the next period date.
The calculator highlights the five days before estimated ovulation plus ovulation day. This reflects the practical fertile window used for cycle timing, but exact timing can vary by cycle.
No. This is a general date estimator and is not reliable contraception. Irregular cycles, recent hormonal contraception, breastfeeding, postpartum changes, PCOS, illness, stress or travel can shift ovulation.
Results are estimates generated locally in your browser from cycle dates and common fertile-window timing. They are for informational purposes only and are not medical advice, fertility treatment, diagnosis or contraception. Ovulation can vary even in regular cycles. Seek professional guidance for irregular or absent periods, known fertility conditions, repeated pregnancy loss, pelvic pain, heavy bleeding, postpartum or breastfeeding cycles, or if you are trying to conceive without success.