How to Use the Period Calculator
Enter the first day of your most recent period, your average cycle length (the number of days from the start of one period to the start of the next), and your average period duration. The calculator will project your next 6 cycles, including predicted period dates, fertile windows, and estimated ovulation days. Use the visual calendar below the results to see all your cycle phases color-coded across upcoming months.
Understanding Your Cycle Phases
A menstrual cycle has four main phases. The menstrual phase (your period) is when the uterine lining sheds, typically lasting 3-7 days. The follicular phase begins on day 1 of your period and ends at ovulation, during which follicles in the ovaries mature. Ovulation occurs mid-cycle when a mature egg is released. The luteal phase follows ovulation and lasts until your next period, typically about 14 days.
Tips for Tracking Your Cycle
- Track your period start date each month to calculate your true average cycle length over time.
- Note any symptoms like cramps, mood changes, or spotting to identify your personal patterns.
- Cycle lengths can fluctuate -- track at least 3-6 months for a more accurate average.
- Factors like stress, travel, diet changes, and exercise can temporarily shift your cycle.
- See a healthcare provider if your cycles are consistently outside the 21-35 day range.