No more wondering “when will my first period come?”

Hi, it's us: Soso, Soso's mom and dad. We are the small family that makes this app, and we read every single message you send us.

One question arrives more than any other. Several times a day, in every language, some version of the same five words:

When will my first period come?

It came up in the quiz too. More than 14,000 of you have taken it, and afterwards a lot of you wrote to ask the same thing, but closer to home. Not what happens to girls in general: what's happening to you.

So we spent the last months building an answer. We cannot tell you the day, and neither can anyone else. What we can do is tell you the months it is most likely to fall in, how close you are, and why. It is the biggest thing we have ever made (besides launching Soso, of course!).

A sneak peek 🌸

We tell you the months

You answer a few questions, and a second later there it is, written on the paper: the months your first period is most likely to land in, and underneath, the reasons we picked them. Not a date, because nobody has one to give you. But not a shrug either.

Most likely between March and September. It stays on your home screen after that, with a little fill that shows how close you are getting, and every time you tell us something new it moves.

The whole app looks different now

Torn paper, polaroids, washi tape, handwriting in the margins. A scrapbook you are keeping about yourself. At night the whole thing goes under a blacklight and glows. If you love it, we will bring it to the rest of the app. If you hate it, please tell us that too.

The questions don't feel like homework

Pictures you pick instead of words you have to find. Cards you drag. A deal at the end that you seal by dragging a piece of tape down with your thumb. And "I'm not sure" is always there, on every question, and it never blocks you.

Your body changes and your mood are in the same place now

The slow stuff about your body used to live in a different part of the app from the face you tap every day. That was silly, so we put them together. On a normal day it is still one tap. When something has changed, the chip is right there.

The tape measure, once a month

A monthly ritual that takes ten seconds. Three measurements in and we can start seeing the shape of your growth.

The Signs tab: a page of everything that already happened 🌱

Every time something happens, we tear off a scrap of paper and write the date on it. The day your first sign showed up. The day you were measured for the first time. The day your growing sped up. The day you got older than your mom was when hers arrived. Nothing on this page can be late or missed, because nothing there is waiting on you. It is just the road behind you, getting longer.

Already have your period?

This version is for you too. We fixed the things that were tripping up period tracking, the calendar now has a legend that explains every colour and every dot, and if you marked days by mistake you can clear several at once. If you want to track body changes as well, turn them on under What I track.

The science, briefly

Your body sends signals for months or years before a first period, and those signals have been measured in thousands of girls. Here is what we read:

• Your chest starting to change. From that first change, a first period usually follows around two and a half years later.
• Your first hair. Roughly one to two and a half years ahead.
• Discharge, the clear or white stuff you find in your underwear. It usually shows up 6 to 12 months before, which makes it one of the most reliable short-term signs there is. It is not gross and it is not a problem. It is your body getting ready.
• Your chest reaching a fuller, grown-up shape. Often less than a year to go.
• Your growth spurt. You grow fastest about a year before your first period, so once your fastest stretch has passed, the clock is quietly running. That is what the tape measure is for. 📏
• Your age, and your mom's age at her first period. These fill in the background when you have not noticed much yet. They are statistics, not observations of you, so we let them nudge the answer but never pretend to be certain.

Two rules underneath all of it. First, we combine these signs instead of picking a favourite, so when two signs disagree the window gets wider and more honest instead of averaging into a confident wrong answer. Second, there is no correct order. Nearly half of girls start chest and hair changes around the same time, so whatever order yours happen in, you are not behind and you are not strange.

Every number behind this comes from published research, and you can read the sources in the app under Medical sources.

How to get it

Seeing the months is free. The questions at the start, the reveal, the window on your home screen and your moods cost nothing, and they always will.

What you pay for once, if you want it, is the part where you keep telling us things: the check-ins, the tape measure, the Signs tab, and an answer that keeps getting sharper. That is the First Period Pack.

• One payment. It is not a subscription. Nothing renews, there is nothing to cancel, and it is yours for good.
• On iPhone, tap Unlock my pack and confirm with your Apple ID. If your phone is part of a family, a grown-up gets an approval request, and the pack is shared with your family once it is bought.
• On Android, the same button opens Google Play and pays with whatever your family has set up there.
• Already have Soso Plus? It is already included. Do nothing.
• Changed phones, or bought it before? Restore purchases on the paywall brings it back for free.
• Not your phone to pay with? There is an Ask a grown-up button that writes the message for you and explains what the pack is, so you do not have to.

What we didn't do on purpose

Before we wrote a single line of code, we decided one thing: we were never going to invent a date.

An app can't tell you the exact day your first period will arrive. Sometimes not even a doctor can. If someone that's not your doctor puts a confident little date on your calendar is guessing and hoping you never check. So we give you months and weeks, and we tell you how sure we are.

Two more things we would rather say out loud than let you find out on your own:

• Not everything you log will visibly move the months. When something new agrees with what you already told us, it makes the answer more certain rather than different. That is the boring, real way this works.
• The answer never slides backwards, and checking in a lot does not move you forward. A girl who logs every week and a girl who logs twice a year get the same answer from the same evidence. This is about your body, not about how often you open the app.

One more thing

We are not finished. This is the first version of something we want to keep making better for years, and the more you tell us, the better we get at telling you.

So if something is wrong, confusing, or missing, tell us. Open the app, go to the Learn tab and tap Talk to Soso, and write whatever is on your mind. It comes straight to us, we read all of it, and it is honestly how this whole thing got built in the first place. 💗