Estimate your ovulation date, fertile window, and next period using your last period date and average cycle length. Results are estimates and do not replace medical evaluation.
Enter your details to view results.
If your cycles vary significantly, you skip periods, are breastfeeding, or recently stopped hormonal birth control, estimates may be less reliable.
This tool uses the calendar method. It cannot confirm ovulation nor should it be used as a contraceptive method.
Estimated projection for your next 4 cycles. Select any cycle to view additional details like peak fertile days and suggested pregnancy test date.
The calculator applies the mathematical calendar method to estimate the ovulation event and fertile window based on the First Day of the Last Menstrual Period (LMP) and average cycle length:
Estimated Ovulation = LMP + Cycle Length − 14 Days
Based on this milestone, key physiological intervals are projected:
Ovulation is the phase of the menstrual cycle in which a mature ovarian follicle releases an egg into the Fallopian tube, where it remains viable for fertilization for approximately 12 to 24 hours.
The menstrual cycle consists of two primary phases separated by ovulation: the follicular phase (variable in length) and the luteal phase (typically constant at 12–14 days before the next period).
The calendar method is a statistical probability model. Follicular phase duration varies due to biological and environmental factors such as stress, weight changes, polycystic ovary syndrome (PCOS), thyroid disorders, or recent contraceptive use.
This tool is educational and informational. It does not provide medical diagnosis nor should it be used for contraception.
Algorithmic model structured by Calculatodo based on clinical guidelines from the following health institutions: