Ovulation Calculator — Fertile Window & Safe Period
Enter the first day of your last menstrual period (LMP) and your average cycle length to automatically calculate your ovulation day, fertile window, and safe period. Results are displayed in an intuitive calendar format to help you understand your menstrual cycle. For health reference only; not medical advice.
Enter Menstrual Information
Fill in your last period date and average cycle length, then click calculate to view the ovulation calendar.
Normal range: 21-35 days
Cycle Calendar
Click "Calculate Ovulation" to generate the calendar.
Period
Fertile Window
Ovulation Day
Safe Period
Frequently Asked Questions
The ovulation period is the time when the ovary releases an egg. It typically occurs about 14 days before your next period. After ovulation, the egg can survive for 12-24 hours, while sperm can survive for 3-5 days in the female body. Therefore, the 5 days before and 1 day after ovulation are considered the fertile window.
The rhythm method (calendar method) has relatively low reliability, especially when menstrual cycles are irregular. The typical-use failure rate is about 24%. It is recommended to combine this with basal body temperature monitoring and cervical mucus observation to improve accuracy, or use more reliable contraception methods.
Count from the first day of your period to the day before your next period starts. A normal cycle is 21-35 days, with 28 days being average. If your cycle is often shorter than 21 days or longer than 35 days, it is recommended to consult a gynecologist.
If your cycle is irregular, it is recommended to track at least 6 months of cycle data and use the average. You can also calculate the safe period range using your shortest and longest cycles separately. The most reliable method is to combine with ovulation predictor kits or basal body temperature monitoring.
The highest conception rate occurs when intercourse happens 2 days before and after ovulation. It is recommended to maintain regular sleep, healthy diet, moderate exercise, and reduce stress. If you have difficulty conceiving (for more than 1 year), it is recommended to consult a reproductive specialist.