Cycle Circle guide
How to track your period and predict your next one
To track your period, note the first day of bleeding each month: that is day 1 of your cycle. Cycle length is the number of days from one day 1 to the next. After three or more cycles you can average them to estimate when your next period will start, and roughly when you ovulate (about 14 days before it). Logging symptoms and mood alongside shows patterns over time. Predictions are estimates, not contraception.
How to count your cycle
- Day 1 is the first day of real bleeding, not spotting. Write down the date.
- Note how many days you bleed. That's your period length, usually 2 to 7 days.
- When the next period starts, count the days since the last day 1. That's your cycle length.
- Repeat for three cycles or more. One cycle tells you little; several show your usual range.
Worked example
Periods started on 3 March, 31 March and 30 April. The cycles were 28 and 30 days long, so the average is 29. The next period is likely around 29 May, give or take a few days.
What is a typical cycle?
The NHS describes a typical cycle as anywhere between 21 and 40 days, with 28 as an average, not a target. It's normal for your cycle to vary by a few days from month to month.
| Phase | Roughly when | What's happening |
|---|---|---|
| Period (menstrual) | Days 1 to 5 | The womb lining sheds |
| Follicular | From day 1 until ovulation | An egg matures; energy often rises |
| Ovulation | About 14 days before the next period | An egg is released |
| Luteal | From ovulation to the next period | PMS symptoms are most common towards the end |
The luteal phase is fairly steady for each person, about 12 to 14 days for most. The follicular phase varies more, which is why a longer cycle usually means later ovulation, not a longer wait after it.
What to log
- Period days and flow: light, medium or heavy.
- Pain and where it is.
- Symptoms: bloating, headaches, breast tenderness, spots, sleep changes.
- Mood and energy, which often follow a pattern across the cycle.
- Basal body temperature (optional), taken first thing each morning. A small sustained rise usually follows ovulation.
Patterns are the point. "I always get headaches two days before my period" is useful to know, and useful to show a doctor.
How period and ovulation predictions work
Trackers estimate the next period by averaging your recent cycle lengths, and estimate ovulation by counting back about 14 days from it. The fertile window is roughly the five days before ovulation and the day after, because sperm can survive for several days.
In Cycle Circle, predictions use up to your last 12 cycles, with recent ones counting more. Until you've logged three, it blends in your usual cycle length from setup (28 days if you're not sure). It shows a range, not a single day, and the range narrows as your cycles become more regular. If you log temperatures, it can use your own luteal length instead of 14 days.
When to see a doctor
Talk to your GP or doctor if:
- your periods are very heavy (soaking through pads or tampons every hour or two, or passing large clots)
- you have severe pain that stops you doing everyday things
- your cycles are often shorter than 21 days or longer than 40, or change suddenly
- you bleed between periods or after sex
- your periods stop for three months or more and you're not pregnant
A log of dates, flow and symptoms makes that appointment much easier. This is general information, not medical advice.
Tracking in Cycle Circle
Cycle Circle is a free, private period tracker in your browser. There's no account, no server and no analytics on your health data.
- Set up: tell it when your last period started and your usual period and cycle length (or use typical values).
- Tap Period started? on the Today tab when it begins, and Log today for flow, symptoms, mood and temperature.
- Check the Calendar for predicted periods and the fertile window, and edit period days if you forgot one.
- See Insights to compare your last six cycles.
- Take it to an appointment: Doctor summary makes a printable summary, and Export CSV gives you the raw data.
An optional PIN lock encrypts your data, and Discreet mode uses neutral wording. Back up to a file to move to another device.
Common mistakes
- Counting from the last day of your period. Day 1 is the first day of bleeding.
- Counting spotting as day 1. Use the first day of real flow.
- Trusting predictions after one cycle. Give it three or more.
- Using an app as contraception. Predictions are estimates. Ask a professional about contraception.
- Only logging dates. Symptoms and mood are what reveal patterns.
- Worrying about a cycle a few days off. Some variation is normal. Big or lasting changes are worth a GP visit.
Questions
How do I calculate my cycle length?
Count the days from the first day of one period to the day before the next period starts. Average three or more cycles for a useful figure.
Is a 35-day cycle normal?
The NHS describes cycles anywhere from 21 to 40 days as typical. If yours changes suddenly or you are worried, speak to your GP.
When do I ovulate?
Usually about 12 to 14 days before your next period starts, not necessarily on day 14. In a 32-day cycle that is around day 18 to 20.
Can a period tracker be used as contraception?
No. Cycle Circle's predictions are estimates and not a method of contraception. Speak to a GP, nurse or sexual health clinic about options.
Is my period data private in Cycle Circle?
Yes. It is stored in your browser only, with no account or server. You can add a PIN lock that encrypts it.
Is Cycle Circle free?
Yes. Cycle Circle is completely free, with predictions, logging, insights, a doctor summary and backup.