Period
Track menstrual cycle and predict next period
These calculators provide general information only and are not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
How to use Period
- 1Enter first day of last period and average cycle length.
- 2The tool estimates next period and upcoming cycle dates.
- 3Also estimates the current phase (follicular / luteal).
Predicting periods: cycle math
next = last first day + cycle length; phase ≈ days since last first dayThe core is cycle length: add one cycle to the last first day for the next expected date. Most people fall in 21–35 days; 28 is common, not a standard.
Knowing length also hints at phase: ovulation ~14 days before next period, follicular before, luteal after—helping explain mood/energy swings.
Good for regular-cycle reminders; if cycles are chaotic, very long, or painful, see a doctor for PCOS/thyroid rather than relying on math.
Frequently asked questions
What cycle length is normal?
21–35 days is common and varies by person. As long as yours is stable, you needn't hit 28.
Why is mine never on time?
Stress, big weight changes, poor sleep, illness all disrupt it. Occasional shifts are normal; chronic irregularity deserves a check.
Can this detect pregnancy?
No. A late period is only one possible sign; confirm with a test. This tool only schedules, not diagnoses.