How to Use the Cycle Calculator
This tool helps you estimate your future menstrual cycles and identify your most fertile days based on your cycle's history.
- 1. Enter Your Last Period Date: Use the date picker to select the first day of your most recent menstrual period. This is the primary data point for the calculation.
- 2. Enter Your Cycle Length: Input the average length of your menstrual cycle in days. The average is 28 days, but this can vary from person to person. For the most accurate prediction, use your own average.
- 3. View Your Estimate: The calculator will instantly show your results, including your estimated next ovulation date, your fertile window, and the predicted start dates for your next three periods.
Frequently Asked Questions
How is ovulation calculated?
Ovulation is the part of the cycle when an egg is released from the ovary. It typically occurs about 14 days *before* the start of the next period. This tool calculates your next period date based on your cycle length and then counts back 14 days to estimate your ovulation day.
What is the "fertile window"?
The fertile window is the time in your menstrual cycle when you are most likely to become pregnant. It includes the day of ovulation and the five days leading up to it. This is because sperm can survive in the female reproductive tract for up to five days. Our calculator highlights this entire 6-day period.
How accurate is this calculator?
This tool provides an estimate based on a regular menstrual cycle. However, many factors such as stress, diet, and lifestyle changes can affect your cycle length and ovulation day, making them vary from month to month. For this reason, the calculator is a great informational guide but should not be used as a form of birth control.
Important Medical Disclaimer
The information and calculations provided by this tool are for educational and informational purposes only. They are not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.