A period tracker that shows the whole cycle
Tap once when your period starts. Add flow, cramps or a bad-mood day if you want. After a few months you can see how long your cycles really run, and when your next period is likely.
A cycle runs from the first day of one period to the day before the next. The NHS gives about 28 days as the average and calls regular cycles of 21 to 35 days normal.[1][2]
Logging the first day of each period is enough to see your own pattern. Her Good Days turns those dates into cycle lengths and an estimated next period, shown as a range of days.
What you can log
In the app, a woman with regular cycles usually sees these five in her Log menu, and can pin or hide any of them:
| Log item | What it records |
|---|---|
| Period | Start and end days |
| Flow or spotting | Light, medium or heavy, and spotting between periods |
| Cramps and PMS | Cramps, bloating, headaches, tender breasts, and how strong[6] |
| Mood | One tap, any time of day |
| Sleep | Bedtime, wake time and how rested you feel |
Water, weight, meals and a journal sit under More.
How the next-period estimate works
The app averages your recent cycle lengths and counts forward from your last period. When your cycles vary, the estimate becomes a wider window, and the app says so. Reviewers of other trackers often complain that predictions miss irregular cycles, so we show the range instead of a single confident date.
Is my cycle normal?
The app doesn't judge your cycle. It shows the numbers, and a doctor is the right person to read them. The NHS and ACOG suggest seeing a doctor if your periods suddenly change, are very heavy, last longer than 7 days, or stop when you're not pregnant.[2][3][4] Period pain that stops you doing your usual daily activities is also worth an appointment.[5]
The doctor report lists your period dates, cycle lengths and logged symptoms on a few pages.
Your cycle changes with you
First periods
Teen mode for ages 13 to 17 keeps the cycle, mood and sleep tools.
Teen mode
Cycles getting longer or shorter
In your 40s, the same log starts to show perimenopause changes.
Perimenopause
Everything else you track
Sleep, food, water and habits sit in the same app.
What you can track
Other life stages
Trying to conceive
Cycle notes and tests to share with your doctor.
Pregnancy
Your week, appointments and symptoms.
Postpartum
Recovery, broken sleep and mood after birth.
Perimenopause
Changing cycles and new symptoms, in one log.
Menopause
Hot flashes, night sweats and sleep.
After menopause
Strength, bones, sleep and medication.
Teens
First periods, with teen mode for 13 to 17.
The features for this stage
The screens you would use most. Every feature in the app
Questions
How long is a normal menstrual cycle?
The NHS puts the average at about 28 days, and calls regular cycles from 21 to 35 days normal. Yours can also vary a little from month to month.
Can I use the period predictions as birth control?
No. The app shows an estimated next period from your past cycles. It can't tell you when pregnancy is unlikely, and it should never be used to prevent one.
Is the period tracker free?
Yes, with full history, charts and the doctor report. There is no premium tier and no trial.
What if my periods are irregular?
Keep logging the first day of each period. The estimate widens to a range when your cycles vary, and the cycle-length chart shows the spread, which is useful to bring to a doctor.
Sources
- NHS: Periods and fertility in the menstrual cycle Checked October 30, 2026
- NHS: Irregular periods Checked October 30, 2026
- ACOG: Heavy menstrual bleeding Checked October 30, 2026
- NHS: Missed or late periods Checked October 30, 2026
- NHS: Period pain Checked October 30, 2026
- NHS: PMS (premenstrual syndrome) Checked October 30, 2026
Spotted an error? Write to [email protected]. How we check health information.