Menstrual Cycle
Track Menstrual Cycle by entering your cycle dates and temperatures. Get predicted ovulation window, fertile days, and cycle phase breakdown.
Formula
Ovulation = Cycle Length - 14 days
Ovulation typically occurs 14 days before the next period. The fertile window is 5 days before through 1 day after ovulation.
Worked Examples
Example 1: Calculate Next Period
Problem:Last period started Jan 15, cycle length 30 days.
Solution:Last period: January 15\nCycle length: 30 days\n\nNext period = Jan 15 + 30 days = February 14\n\nOvulation day = 30 - 14 = day 16\nOvulation date = Jan 15 + 16 = January 31\n\nFertile window: January 26 - February 1
Result:Next period: February 14, Ovulation: January 31
Example 2: Determine Fertile Window
Problem:28-day cycle, last period Jan 1.
Solution:Cycle length: 28 days\nOvulation day: 28 - 14 = day 14\nOvulation date: January 14\n\nFertile window:\n5 days before: January 9\nOvulation day + 1: January 15\n\nMost fertile: January 12-14\n(2 days before through ovulation day)
Result:Fertile window: January 9-15
Example 3: Track Cycle Day
Problem:Last period Feb 1, today is Feb 20, 26-day cycle.
Solution:Last period: February 1\nToday: February 20\nDays since last period: 19\n\nCycle day: 19 (if within first cycle)\n\nFor 26-day cycle:\nOvulation around day 12 (26-14)\nCurrently in luteal phase\nNext period: Feb 1 + 26 = February 27
Result:Day 19 of cycle (luteal phase)
Frequently Asked Questions
How long is a normal menstrual cycle?
Normal cycles range from 21-35 days, with 28 days being average. Cycles are measured from the first day of one period to the first day of the next. Variation of a few days between cycles is normal. Consistently irregular cycles may warrant medical evaluation.
What are the phases of the menstrual cycle?
1) Menstrual (days 1-5): Uterine lining sheds. 2) Follicular (days 1-13): Egg develops in ovary, estrogen rises. 3) Ovulation (day 14): Egg released. 4) Luteal (days 15-28): Progesterone rises, uterus prepares for potential pregnancy.
When should I see a doctor about my cycle?
Consult a doctor if: periods stop for 3+ months (not pregnant), cycles shorter than 21 or longer than 35 days consistently, extremely heavy bleeding, severe pain interfering with daily life, bleeding between periods, or sudden changes in cycle pattern.