How to Track Your Menstrual Cycle (2026)
By Rui Barreira · Last updated: 18 June 2026
Tracking your menstrual cycle helps you understand your body's patterns, anticipate your next period, identify fertile windows, and spot irregularities early. A typical cycle runs 21–35 days, but variation between individuals — and between months for the same person — is normal. Consistent tracking over two or three months gives you a reliable personal baseline.
What to Record Each Cycle
The minimum data worth logging is the first day of your period (cycle day 1) and the last day of bleeding. From this alone you can calculate cycle length and period duration over time. Additional data points improve accuracy and usefulness:
| Data point | Why it matters |
|---|---|
| Cycle start date (day 1 of bleeding) | The anchor for all other calculations |
| Period duration (days of bleeding) | Identifies unusually short or long periods |
| Flow intensity (light / medium / heavy) | Flags changes that may warrant clinical attention |
| Symptoms (cramps, mood, spotting) | Helps correlate patterns with cycle phase |
| Basal body temperature (BBT) | Confirms ovulation — rises ~0.2–0.5°C after ovulation |
| Cervical mucus texture | Peaks in elasticity around ovulation (egg-white consistency) |
Understanding Cycle Phases
A menstrual cycle has four phases. The follicular phase starts on day 1 (the first day of bleeding) and runs until ovulation. Ovulation typically occurs around day 14 in a 28-day cycle, but shifts with cycle length — a rough estimate is cycle length minus 14 days. The luteal phase follows ovulation and lasts roughly 12–16 days; if fertilisation does not occur, progesterone drops and menstruation begins. The length of the luteal phase is relatively stable for any given person, so most cycle-length variation happens in the follicular phase.
The fertile window spans the five days before ovulation and the day of ovulation itself, since sperm can survive up to five days in the reproductive tract. Identifying this window accurately requires tracking multiple signals — calendar calculations alone are an approximation.
When to Seek Medical Advice
Tracking makes it easier to notice patterns that warrant attention. Consult a healthcare provider if you observe: cycles consistently shorter than 21 days or longer than 35 days, periods lasting more than seven days, very heavy flow (soaking more than one pad or tampon per hour for several consecutive hours), periods that stop for three or more months without pregnancy, or severe pain that interferes with daily activities.
Use the Menstrual Cycle Calculator to log your last period date and average cycle length — it predicts your next period, fertile window, and ovulation date instantly, with no account required.
Frequently Asked Questions
- Is this tool free?
- Yes — completely free, no signup required. All processing happens in your browser.
- Does the tool work offline?
- Once loaded, most features work without an internet connection since everything runs client-side.