About this Calculator
Tracking ovulation is one of the most effective ways to identify your most fertile days. This tool estimates your fertile window and ovulation day to help you plan.
Formula & Calculations
Mathematical Formula
Ovulation Day = LMP + Cycle Length - 14 Days
Estimates fertile window 5 days prior to and 1 day after ovulation.
How to Calculate Step-by-Step
1
Identify LMP
Enter the start date of your last cycle.
2
Deduct luteal offset
Subtract 14 days from projected next cycle start.
How to Use & Best Practices
Input the first day of your last period and average cycle length.
Frequently Asked Questions
When is the fertile window?
The 5 days leading up to ovulation and the day of ovulation.