Menstrual Cycle & Period Calculator
Track your cycle, predict your next period, and estimate your most fertile window.
Next Period Starts:
Estimated Ovulation Day:
Fertile Window:
Estimated Due Date (If conception occurs):
Understanding Your Menstrual Cycle
A menstrual cycle is measured from the first day of one period to the first day of the next. While the average cycle is 28 days long, it is perfectly normal for it to range between 21 and 35 days. Tracking your cycle helps you understand your body's unique rhythm, identifies patterns of ovulation, and assists in family planning.
How the Calculation Works
This calculator uses the standard calendar method to estimate your future dates based on the averages you provide:
- Next Period: Calculated by adding your average cycle length to the start date of your last period.
- Ovulation: Typically occurs about 14 days before your next period begins (the luteal phase is usually constant at 14 days).
- Fertile Window: This includes the day of ovulation and the five days leading up to it, as sperm can survive inside the female reproductive tract for several days.
Example Calculation:
If your last period started on October 1st and you have a 30-day cycle:
- Next Period: October 31st
- Ovulation Day: October 17th (31 minus 14)
- Fertile Window: October 12th – October 17th
The Phases of Your Cycle
1. Menstrual Phase: The first day of your period. This is when the uterine lining is shed.
2. Follicular Phase: Starts on day one and ends with ovulation. During this time, estrogen levels rise as your body prepares an egg for release.
3. Ovulation Phase: The release of a mature egg from the ovary. This is the peak time for fertility.
4. Luteal Phase: The time between ovulation and the start of the next period. Progesterone levels rise to thicken the uterine lining for a possible pregnancy.
Why Cycle Tracking Matters
Consistent tracking is the best way to identify irregularities. If your cycle is frequently shorter than 21 days or longer than 35 days, or if your periods last longer than 7 days, it is advisable to consult a healthcare professional. Tracking also provides essential data if you are trying to conceive or monitoring symptoms related to PMS or PMDD.