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Next period due date · Estimated ovulation date · 6-month calendarPeriod Calculator
If you enter your last period start date and cycle, it provides your next period due date, estimated ovulation date, and a 6-month period calendar.
🗓️ Next due date📅 6-Month Calendar📊 Periodic Analysis⏰ D-Day
📝 Enter period information
Last period start date
menstrual cycle28th
일
20th28th35 days45 days
menstrual period5 days
일
2 days5 days7 days10 days
💡 If your menstrual cycle is irregular, please enter your average cycle over the last 3 to 6 months.
📊 Calculation result
🗓️
After entering menstrual information
Calculate your period datePlease press .
Next period due date
—
—
My next period is scheduled to end.—
Expected ovulation date—
fertile period—
Periodic classification—
Until the next period—
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What is a period calculator?
The period calculator calculates the expected date of your next period, ovulation date, and fertile period based on your last period start date and cycle, and predicts your schedule for the next six months. It can be used as a basic tool for pregnancy planning or health management.
Normal menstrual cycle
- Normal range: 21~35 days (average 28 days)
- Frequent menstruation: Less than 21 days → Consultation with an OB/GYN recommended
- Oligomenorrhea: Exceeding 35 days → Consultation with an OB/GYN recommended
- Amenorrhea: No period for more than 3 months → Consult an OB/GYN immediately
Main causes of irregular menstruation
- Stress, excessive exercise, rapid weight changes
- Thyroid dysfunction, polycystic ovary syndrome (PCOS)
- Pregnancy, pre-menopause (menopause)
⚠️ This calculator is for reference only. If your menstrual cycle is irregular or you experience any unusual symptoms, please consult a gynecologist.
Frequently Asked Questions
What is a normal menstrual cycle?
A normal menstrual cycle is 21 to 35 days, with an average of 28 days. Individual differences exist, and even the same person may experience slight variations each month. If your cycle is shorter than 21 days or longer than 35 days, consulting a gynecologist is recommended.
What are the reasons for a late period?
Causes include stress, excessive exercise, rapid weight changes, thyroid abnormalities, polycystic ovary syndrome (PCOS), and pregnancy. If it is delayed by more than two weeks, it is recommended to take a pregnancy test first and consult an OB/GYN.
Why does Premenstrual Syndrome (PMS) occur?
During the 7 to 14 days before menstruation, hormonal changes (decreased estrogen and progesterone) can cause mood swings, fatigue, abdominal bloating, and breast pain. If symptoms are severe, it is recommended to consult a gynecologist.
Can I make my menstrual cycle regular?
Regular sleep, maintaining a healthy weight, managing stress, and a balanced diet are helpful. Taking iron, magnesium, and omega-3s can also be beneficial. If your sleep is consistently irregular, consult a gynecologist.