Ovulation Calculator
A simple, math-based tool to predict your ovulation day and fertile window based on your cycle.
How to Use
- Step 1: Enter the first day of your last period and your average cycle length.
- Step 2: View your predicted ovulation day and fertile window below.
- Step 3: Explore your cycle visually in the calendar.
How This Calculator Works
1. Enter Your Data
Input the start date of your last menstrual period and the average length of your menstrual cycle in days.
2. View Your Results
The tool automatically calculates your estimated ovulation day and fertile window based on the standard formula.
3. See the Calendar
The calendar view highlights these key dates, providing a clear visual representation of your cycle's phases.
Disclaimer
This tool provides a mathematical estimation based on the data you provide. It is not medical advice. The calculations are based on a regular cycle and may not be accurate for everyone. For health-related concerns, please consult a qualified medical professional.
Frequently Asked Questions
How is the ovulation day calculated?
This tool uses a standard mathematical formula: it subtracts 14 days from your average cycle length and adds that number of days to your last period start date. This is based on the assumption that the luteal phase (post-ovulation) is typically 14 days long.
What is the fertile window?
The fertile window is the time in your cycle when conception is possible. This calculator defines it as the five days leading up to ovulation, the day of ovulation itself, and the day after.
Is my data private?
Yes. All information you enter is stored exclusively in your browser's local storage. Your data is never sent to or stored on our servers, ensuring complete privacy.