Your Fertile Window, Explained

Many people assume you can only conceive on the day of ovulation. The fertile window actually starts several days earlier, because sperm can survive in the reproductive tract for up to five days waiting for an egg to be released.

An egg, once released, is only viable for around 12 to 24 hours. So the highest odds of conception come from sex in the five days before ovulation and on the day itself. That makes a six-day window, with the two days immediately before ovulation generally considered the most fertile.

Why timing is approximate

Ovulation doesn't fall on the exact same cycle day every month, even for people with very regular cycles. Stress, illness, travel, and other factors can shift it earlier or later. So any fertile-window prediction is an estimate based on your average cycle length and luteal phase.

Signs to watch alongside the calendar

Many people also notice physical signs around ovulation: a change in cervical mucus (becoming clearer and more stretchy), a slight rise in basal body temperature after ovulation has occurred, or mild one-sided pelvic twinges. None of these are precise on their own, but combined with cycle tracking they can help narrow down your personal pattern.

OurPeriod & Ovulation Tracker marks your estimated fertile window and peak ovulation day directly on a calendar based on the inputs you provide.