Calculate your menstrual cycle length from two period start dates.
Normal cycle length ranges 21-35 days. The average is 28 days, but studies show fewer than 15% of women actually have a 28-day cycle. Cycles of 25-30 days are most common. Knowing your cycle length is critical for accurately predicting ovulation, since ovulation occurs approximately 14 days BEFORE your next period regardless of cycle length.
Medical Disclaimer: This tool is for educational purposes only and should not replace professional medical advice. Always consult a qualified healthcare provider.