Step 1
Mark day one
Tap + Log, then Period, on the day it starts. Add the flow if you want to, or leave it.
Ages 13 to 17
Your first periods, without the guesswork
Mark the day your period starts, note cramps or a rough day, and the app keeps count. Teen mode keeps it to what matters at 13 to 17.
Period started
Day 1 · light flow
Your usual gap
29 days
What teen mode includes
Teen mode turns on at 13 to 17 from the age band you pick at the start. Here is what it keeps and what it leaves out.
| In the app | Teen mode |
|---|---|
| Period start and end days, flow | On |
| Cramps and PMS, mood, energy, sleep, water | On |
| A private journal and short articles about periods and growing up | On |
| The wellness shop, its banners and marketing email | Off |
| Weight-loss and calorie goals | Off |
| Pregnancy tracking, fertile-window days and anything that scores days as lower or higher chance | Off |
How it works, in three taps
Step 2
Note a rough day
Cramps, a low mood or a bad night take one tap each. Over a few months you can see if they line up with your period.
Step 3
See when the next one is likely
After a few periods the app shows your usual gap, so you know which week to pack pads or a cup.
Why write it down?
Early cycles jump around, so "when is my next one?" is hard to answer from memory. A few months of dates shows your usual gap, and the app gives a likely window for the next period so you can keep pads or a cup in your bag that week.
It also helps when something feels wrong. Saying "my last 3 periods lasted 9 days and I missed school twice for cramps" gives a doctor much more to go on.
Worth telling a doctor or school nurse
- no period by 15
- periods that last more than 7 days, or soak through a pad or tampon every 1 to 2 hours
- cramps that over-the-counter pain relievers don't help, or that keep you home from school
- periods that stop for more than 3 months, or come more often than every 21 days[2]
For parents and carers
The app asks for an age band, never a date of birth. Under 13 can't sign up. Teen accounts see no products and no marketing messages. Your teen can start as a guest, which keeps everything on her phone.
Read the privacy policy or see how the app treats data.
Other life stages
At 18 the full app opens up, and her history comes with her.
Periods and cycle
Period dates, flow, cramps and PMS.
Period day 2
Medium flow
Trying to conceive
Cycle notes and tests to share with your doctor.
Ovulation test
8:10 AM · logged
Pregnancy
Your week, appointments and symptoms.
Week 24
16 weeks to go
Postpartum
Recovery, broken sleep and mood after birth.
Slept 3 h 40 m
in 2 stretches
Perimenopause
Changing cycles and new symptoms, in one log.
Cycle day 38
Longer than usual
Menopause
Hot flashes, night sweats and sleep.
Night sweats
3:10 AM · mild
After menopause
Strength, bones, sleep and medication.
Strength
12 min done
The features for this stage
The screens you would use most. Every feature in the app
Period calendarPeriod days, symptoms and the next period as a range.
Mood trackerMood, energy and stress in a tap, a journal and breathing.
Sleep trackerBedtime, wake-ups and night sweats, side by side.
PrivacyWhat stays on your phone, and how to delete it.
The Log buttonThe five things you log most, one tap away.
Habit trackerYour own habits, with streaks that forgive a missed day.
Questions
How old do you have to be to use Her Good Days?
13 or older. The app asks for an age band at the start, and anyone under 13 sees a stop screen.
What is different in teen mode?
Ages 13 to 17 get the cycle, cramps and PMS, mood and sleep tools, plus articles to read. There is no shop, no marketing email, no weight-loss or calorie goal, and no pregnancy or fertile-window features.
When do periods usually start?
The NHS says most girls start their periods at about 12, and they can start as early as 8. ACOG adds that some girls don't start until 16, and that's normal too.
Does it cost anything?
No. Every feature is free and there is nothing to subscribe to.
Sources
- NHS: Starting periods Checked October 30, 2026
- ACOG: Your first period Checked October 30, 2026
Spotted an error? Write to [email protected]. How we check health information.