Ovulation Calculator

Find your fertile window and best days to conceive based on your cycle.

First Day of Last Period

Cycle Length (days)

Period Length (days)

How to use

Enter the first day of your most recent period.
Set your average cycle length — 28 days is the average but many women range from 21–35 days.
Enter how many days your period typically lasts.
Click Calculate to see your ovulation date and fertile window.
Ovulation typically occurs 14 days before your next period starts.
The fertile window is 5 days before ovulation plus ovulation day itself — sperm can survive up to 5 days.
The 3-month chart shows upcoming cycles, fertile windows, and ovulation days.