Ovulation Calculator
Ovulation day and fertile window from your cycle length.
Frequently asked questions
When does ovulation happen?
In a typical cycle, ovulation occurs about 14 days before the next period (not necessarily mid-cycle). So we estimate it as cycle length minus ~14 days.
What is the fertile window?
These are the days conception is most likely — roughly the 5 days before ovulation and the day after, because sperm can survive for several days.
How reliable is the estimate?
This is a calendar-method estimate. Ovulation varies between cycles; for closer tracking use basal body temperature or ovulation test kits.