CycleFlow - Period Tracker
CycleFlow is a period diary with a calendar. You record the day your period starts and the day it ends, and on any day you can note symptoms such as cramps, headache or low mood, along with basal body temperature, weight and a short note. From your own records it works out your average cycle and period length and marks an estimated next period, ovulation day and fertile window on the calendar.
It is meant for anyone who wants to understand their own pattern: to know roughly when the next period is likely, to notice symptoms that tend to appear before it, or to have clear dates and notes ready when talking to a doctor or nurse. The graphs make it easy to see how regular your cycles are and how your temperature and weight change over time.
Everything stays in your browser. There is no account and nothing is uploaded.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use CycleFlow
- Read the notice. When you first open CycleFlow on the web, a disclaimer explains that predictions are estimates and not for contraception or pregnancy planning. You can reopen it from Settings.
- Record a period. Open the Record tab, choose the date, and tap Start Period on the first day. When it finishes, choose the last day and tap End Period.
- Add symptoms and measurements. On the same screen, tap any symptoms you have (abdominal pain, headache, back pain, swelling, breast tenderness, irritability, mood down or fatigue), enter basal temperature in °C and weight in kg if you track them, add a note, and tap Save Record.
- Check the calendar. The Calendar tab shows the estimated next period and how many days until it. Coloured days mark the predicted period, ovulation day and fertile window. Tap a day to see its records.
- Review the graphs. The Graph tab has Cycle, Basal Temp, Weight and Symptoms views, with average, shortest and longest cycle, temperature and weight ranges, and how often each symptom appeared in the last three months.
- Adjust cycle settings. In Settings, open Profile Settings. Until you have enough records, you can set your usual cycle and period length; the luteal phase length (default 14 days) can always be changed.
Features
- Period start and end recording
- Eight common symptoms to tick, plus notes
- Basal body temperature (°C) and weight (kg) log
- Average cycle and period length calculated from your records
- Calendar with estimated next period, ovulation day and fertile window
- Countdown to the estimated next period
- Graphs of cycle length, temperature, weight and symptom frequency
- Adjustable cycle, period and luteal phase lengths
- Data saved in your browser, no account
Understanding your menstrual cycle
How cycle length is counted
A cycle is counted from the first day of one period (the first day of real bleeding, not spotting) to the day before the next period starts. Cycles in adults commonly range from about 21 to 35 days, and it is normal for the length to vary by a few days from month to month. Periods typically last two to seven days. Recording the first day accurately matters most, because every average and estimate is built on it.
Why predictions are only estimates
Calendar predictions assume your next cycle will be about as long as your average. Stress, illness, travel, changes in weight or exercise, breastfeeding and the years around puberty and menopause can all shift a cycle. The ovulation estimate here works backwards from the expected next period using the luteal phase (by default 14 days), and the fertile window is the five days before ovulation plus the day after. Real ovulation can happen earlier or later, which is why calendar methods alone are not reliable for avoiding or achieving pregnancy. No day on a calendar is guaranteed to be infertile.
What basal temperature can show
Basal body temperature is your resting temperature measured right after waking, before getting up. Many people see a small, sustained rise of a few tenths of a degree after ovulation. The rise confirms ovulation only after it has happened, and readings are easily affected by poor sleep, alcohol, illness or measuring at different times. If you track it, use the same thermometer at the same time each morning and look for patterns over several cycles rather than single readings.
Tracking symptoms
Noting symptoms over a few months can reveal patterns, such as headaches or low mood in the days before a period. This can help you plan ahead and gives a doctor concrete information if symptoms are troublesome.
When to talk to a professional
Consider seeing a doctor or nurse if your periods stop unexpectedly, your cycles are consistently shorter than about 21 days or longer than about 35, bleeding is very heavy or lasts more than about a week, you bleed between periods or after sex, or pain stops you doing everyday things. Seek urgent care for sudden severe pain or very heavy bleeding with dizziness.
Frequently asked questions
Where is my data stored?
Only in this browser on this device. There is no account and nothing is uploaded. Clearing browser data, using a private window or switching browsers or devices means your records won't be there.
Can I use CycleFlow for contraception or to plan a pregnancy?
No. The predicted period, ovulation day and fertile window are rough calendar estimates. Talk to a doctor, nurse or pharmacist about contraception and fertility.
How many records do I need for good estimates?
At least two recorded period starts are needed to calculate a cycle length. More cycles give a more representative average.
What does a grey day on the calendar mean?
Only that the day falls outside the predicted period, ovulation day and fertile window. It does not mean pregnancy is impossible on that day.
Can I record temperature in °F or weight in pounds?
Not at the moment. Temperature is recorded in °C and weight in kg.
How is the web version different from the phone app?
Recording, the calendar and graphs work the same. The iPhone and Android apps can also send a notification before your estimated period and a daily pill reminder; the web version sends no notifications.
Limitations of the web version
- No notifications or pill reminders on the web
- Temperature in °C and weight in kg only
- Only the next cycle is predicted
- Data stays in one browser and is not backed up
Disclaimer
CycleFlow is a personal record-keeping tool. It is not a medical device and does not provide medical advice, diagnosis or treatment. Predicted periods, ovulation and fertile days are estimates and must not be used as a method of contraception or to plan pregnancy. If you have concerns about your health, please consult a doctor.
Phone app
CycleFlow is also available as an app for phones and tablets: