Irregular Menstrual Cycle Calculator & Guide
An irregular cycle varies by more than 7–9 days between cycles. Tracking is still possible — and often clarifying.
How to track irregular cycles
Log day one of every period, plus any ovulation signs (cervical mucus, basal body temperature, LH tests). After 3–6 cycles you'll see a pattern.
Estimating ovulation with irregular cycles
Don't rely on calendar math. Use LH ovulation strips daily from cycle day 10, plus BBT tracking. Cervical mucus changes (egg-white texture) are the most reliable real-time signal.
When to consult a clinician
Cycles shorter than 21 days, longer than 35 days, missed periods without pregnancy, or wide variation month to month. Common causes: PCOS, thyroid, perimenopause, stress.