Home / Health / Period Calculator
Period Calculator
Predict your next period, ovulation, and fertile window. Understand your cycle and plan ahead with confidence.
Understanding Your Menstrual Cycle
Your menstrual cycle is more than just your period. It's a complex interplay of hormones that prepares your body for pregnancy each month. A "normal" cycle is anywhere from 21 to 35 days long, with bleeding lasting 2 to 7 days.
💡 Expert Tip from Sarah Jenkins, RD
Track more than just dates. Note your symptoms like mood swings, cravings, and energy levels. This can help you identify patterns (like PMS) and distinguish normal fluctuations from potential health issues.
The 4 Phases of Your Cycle
- Menstrual Phase (Days 1-5): The shedding of the uterine lining. Estrogen and progesterone are low.
- Follicular Phase (Days 1-13): The body prepares an egg for release. Estrogen rises, boosting energy and mood.
- Ovulation (Day 14): The egg is released. This is your peak fertility window.
- Luteal Phase (Days 15-28): The body prepares for a potential pregnancy. If no pregnancy occurs, hormone levels drop, leading to PMS and eventually your period.
⚠️ Common Mistake: Assuming Day 14 Ovulation
Not everyone ovulates on Day 14. If you have a 30-day cycle, you likely ovulate around Day 16. If you have a 24-day cycle, it could be Day 10. This calculator adjusts based on your input cycle length.
Frequently Asked Questions
How is the next period calculated?
The calculator adds your average cycle length (default 28 days) to the start date of your last period. For example, if your last period started on Jan 1st and your cycle is 28 days, your next period is estimated to start on Jan 29th.
What is a normal cycle length?
A normal menstrual cycle ranges from 21 to 35 days. The average is 28 days. Teenagers may have cycles ranging from 21 to 45 days.
Can stress delay my period?
Yes, stress can disrupt the hormones that regulate your cycle, leading to a delayed or missed period. Other factors include weight changes, excessive exercise, and certain medications.