Enter your last period and cycle length. We'll plot the next six months — periods, fertile windows, and ovulation days, all at a glance.
The fertile window is the 5 days before ovulation plus ovulation day — that's when intercourse can lead to pregnancy. Wilcox 1995 (NEJM) is the foundational study; conception probability is highest 2–3 days before ovulation.
Calendar math assumes consistent cycles. If yours vary by more than a week, layer this with ovulation tests or basal body temperature tracking.