Health Tools • Calculators

Ovulation & Fertile Window

Use this tool for general educational estimation. Results are not a diagnosis.

First day of last period Average cycle length (days)

Enter the date and cycle length.

Cycle reference: Most menstrual cycles are about 21–35 days. Ovulation timing varies, so the fertile-window dates are calendar estimates only.

Calendar estimate only; cycles vary and this is not contraception or a guarantee of pregnancy.