Enter your period start dates — get an evidence-based assessment of cycle length, regularity, and pattern
Evidence Base
Munro MG, Critchley HOD, Fraser IS; FIGO Menstrual Disorders Committee. The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions. Int J Gynaecol Obstet. 2018;143(3):393–408. — Primary source for all FIGO thresholds used in this tool: normal frequency 24–38 days; regularity criteria by age group.
Jain V, Munro MG, Critchley HOD. Contemporary evaluation of women and girls with abnormal uterine bleeding: FIGO Systems 1 and 2. Int J Gynaecol Obstet. 2023;162 Suppl 2:29–42. — 2023 update confirming FIGO System 1 parameters and PALM-COEIN classification.
Munro MG, Balen AH, Cho S, et al. The FIGO ovulatory disorders classification system. Int J Gynecol Obstet. 2022;159:1–20. — Defines ovulatory disorder spectrum and its menstrual manifestations.
ACOG Committee Opinion No. 651. Menstruation in girls and adolescents: using the menstrual cycle as a vital sign. Obstet Gynecol. 2015;126(6):e143–e146. — Establishes the menstrual cycle as a vital sign in clinical practice.
Bull JR, Rowland SP, Berglund Scherwitzl E, et al. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. NPJ Digit Med. 2019;2:83. — Large digital cohort: mean cycle 29.3 days; confirms population-level variability.
Harlow SD, Lin X, Ho MJ. Analysis of menstrual diary data across the reproductive life span. J Clin Epidemiol. 2000;53:722–733. — Within-woman cycle variability data across age groups.
FIGO normal ranges used in this tool: Frequency: 24–38 days. Regularity (age 26–41): variation ≤7 days = regular. Regularity (age 18–25 or 42–45): variation ≤9 days = regular. Infrequent: >38 days. Frequent: <24 days.
Enter Your Period Start Dates
Enter age above
Enter the first day of each period, most recent first (Row 1 = your most recent period). Enter at least 2 dates. Up to 13 dates = 12 cycles analyzed.
Cycle Length Chart
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Period Start
Next Period Start
Cycle Length
Assessment
Clinical Assessment
Important: This tool provides an educational assessment based on published FIGO criteria. It does not diagnose any medical condition. Abnormal cycle patterns can have many causes — hormonal, structural, and systemic — and require clinical evaluation. If your cycles are consistently outside the normal range, consult your ObGyn or healthcare provider. This tool does not replace clinical judgment.
