Period Cycle Tracker
Predict your next period, fertile window, and ovulation day. All data stays in your browser — completely private.
Your Cycle Details
These predictions are based on average cycle patterns and are for general informational purposes only. Actual cycles can vary. For medical advice, consult your healthcare provider.
About the Menstrual Cycle
The menstrual cycle is a monthly series of changes a woman's body goes through in preparation for the possibility of pregnancy. The average cycle is 28 days, but anywhere from 21 to 35 days is considered normal.
Menstrual Phase (Days 1–5)
The uterine lining sheds, causing bleeding. This is day 1 of your cycle.
Follicular Phase (Days 1–13)
Estrogen rises as the body prepares to release an egg. Energy and mood often improve.
Ovulation (Around Day 14)
A mature egg is released. The 5 days before and day of ovulation are the most fertile.
Luteal Phase (Days 15–28)
Progesterone rises to prepare the uterus. If no pregnancy, levels drop and the cycle restarts.
Frequently Asked Questions
How accurate are these predictions?
Predictions are most accurate for regular cycles. Stress, illness, travel, and lifestyle changes can shift your cycle. Track a few months for better estimates.
Is my data stored anywhere?
Your data is saved only in your browser's localStorage. Nothing is sent to any server. Clearing your browser data will erase it.
What is a "normal" cycle length?
Cycle lengths between 21 and 35 days are considered normal. The average is 28 days, but significant individual variation is common.
When is the fertile window?
Typically 5 days before ovulation and the day of ovulation itself. For a 28-day cycle, ovulation occurs around day 14.