Period Calculator
Enter your last period start date and average cycle length to predict your next 12 period dates.
Understanding Your Period Cycle
How Is Your Next Period Calculated?
Your next period date is estimated by adding your average cycle length to the first day of your last period. A typical menstrual cycle ranges from 21 to 35 days, with 28 days being the average. However, every woman's cycle is unique — factors like stress, diet, exercise, and health conditions can cause variations. This calculator uses a simple arithmetic model. For more accurate predictions that adapt to your individual patterns, Cyla's AI-powered tracking learns from your history to improve accuracy over time.
What Affects Cycle Regularity?
Several factors can influence your menstrual cycle length and regularity: • Stress and sleep quality — Cortisol can delay ovulation, pushing your period later. • Diet and exercise — Significant changes in weight or intense training can affect hormones. • Age — Cycles tend to be irregular during puberty and perimenopause. • Health conditions — PCOS, thyroid disorders, and endometriosis can cause irregular cycles. • Medications — Hormonal contraceptives, some antidepressants, and other drugs may affect timing.
When Should You See a Doctor?
While some cycle variation is normal, you should consult a healthcare provider if: • Your cycle is consistently shorter than 21 days or longer than 35 days • You miss three or more periods in a row • You experience heavy bleeding (soaking through a pad or tampon every hour) • You have severe pain that interferes with daily activities • You notice bleeding between periods Cyla's Health Report feature can generate detailed cycle summaries to share with your doctor.
Frequently Asked Questions
Get Automatic Period Predictions
Stop guessing. Cyla's AI learns your unique cycle and predicts your period with up to 97% accuracy. Free to download.
