Period Calculator

Record the first day of each period as Day 1. Count the days until your next period starts — that is your cycle length. The average is 28 days but anywhere from 21–35 days is considered normal. Tracking for 3–6 months gives a more accurate average.

Ovulation typically occurs 14 days before your next period. For a 28-day cycle, this is around Day 14. The fertile window spans about 5 days before ovulation plus ovulation day itself — roughly Days 10–15. Sperm can survive up to 5 days in the reproductive tract.

Yes. Normal cycle length ranges from 21 to 35 days. Cycles longer than 35 days or shorter than 21 days, or irregular cycles, may warrant a visit to a gynaecologist, especially if you are trying to conceive or are experiencing other symptoms.

Common causes include stress, significant weight changes, polycystic ovary syndrome (PCOS), thyroid disorders, anaemia (common in Nigeria due to dietary iron deficiency), and extreme exercise. Hormonal contraceptives also alter cycle patterns.

No. The rhythm method based on predicted fertile windows has high failure rates (up to 25% per year with typical use). Ovulation timing varies and stress or illness can shift it unpredictably. Use reliable contraception and consult a healthcare provider.