The average menstrual cycle is 28 days, though normal cycles range 21-35 days. Ovulation typically occurs around day 14 (mid-cycle). The fertile window is approximately days 10-17. Track your cycle to predict periods and fertile days.
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📅 Menstrual Cycle Calculator
Calculate and predict your menstrual cycle, ovulation date, and fertile window. Track period regularity and plan accordingly.
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✨ Your Result
🦉Owl's Explanation
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✅ Trusted Tool
Educational tool only — not a substitute for medical advice or reliable contraception. Cycle prediction is approximate. No sign-up needed.
🤔 How Does This Work?
Predicts next period: last period + cycle length
Ovulation estimated: cycle length - 14 days from period start
Fertile window: 5 days before to 1 day after ovulation
❓ Frequently Asked Questions
What is the fertile window?▼
The fertile window is the days in your cycle when pregnancy is possible — typically 5 days before ovulation plus the day of ovulation itself (about 6 days total). Sperm can survive up to 5 days; the egg survives 12-24 hours after release.
Why do cycles vary in length?▼
Cycle length is influenced by stress, weight changes, illness, travel, medications, and underlying health conditions. Some natural month-to-month variation is normal. Consistently irregular cycles (varying by 7+ days) may warrant a doctor's consultation.
The fertile window is the days in your cycle when pregnancy is possible — typically 5 days before ovulation plus the day of ovulation itself (about 6 days total). Sperm can survive up to 5 days; the egg survives 12-24 hours after release.
Why do cycles vary in length?▼
Cycle length is influenced by stress, weight changes, illness, travel, medications, and underlying health conditions. Some natural month-to-month variation is normal. Consistently irregular cycles (varying by 7+ days) may warrant a doctor's consultation.