Tallmark Health, Safety and Estimate Disclaimer
Version 1.0
Effective date: 10 October 2026
Last updated 10 October 2026
In short
Tallmark is a journal and a game. It is not a medical device and it does not give medical advice, a diagnosis or treatment.
Your Predicted adult height is an estimate, shown with a likely range. It is not clinically calibrated, and your adult height may be outside the range. It is not a promise.
Nothing in Tallmark makes you taller. No exercise, food, supplement, amount of sleep or posture adds centimetres or makes bones longer.
Chat with Tally's answers are written by AI. They can be wrong, and they are not medical advice. Do not rely on them for anything important.
If you are worried about your growth, your body or how you feel, talk to a doctor or another health professional.
In an emergency, call your local emergency number (111 in New Zealand, 000 in Australia, 999 or 112 in the UK and Ireland, 911 in the US and Canada). More help: If you need help now (https://sites.google.com/view/tallmark/safety-resources).
This disclaimer is part of the Terms of Use (https://sites.google.com/view/tallmark/terms-of-use). It was written by New Version Ltd, the company that makes Tallmark.
1. What Tallmark is, and what it is not
Tallmark helps you record your height and a few everyday habits (movement, meals, sleep, water, mood and weight), and shows you general information about growing up.
It is not:
a medical device, or a replacement for a doctor, nurse, dietitian, physiotherapist or counsellor;
a way to diagnose, treat or rule out any condition, including growth problems, puberty that is early or late, eating disorders, sleep problems or mental-health problems;
a crisis or emergency service.
Nobody at Tallmark sees what you enter, so nobody at Tallmark can notice if something is wrong. That includes the chat: questions you send to Chat with Tally are answered by an AI and are not read by a person at Tallmark.
2. Your Predicted adult height
The Quest screen shows your Predicted adult height as one number, such as 177 cm, and the Growth tracker shows it with a likely range, such as likely 172–183 cm, and the path to it year by year. Those short labels do not carry the details, so here they are.
It is an estimate, and it is uncalibrated
The prediction and its range are worked out from published population methods using what you entered: your age, sex assigned at birth, height, weight (if you added it), your parents' heights, and your answers about puberty.
"Uncalibrated" means we have not tested how often real people's adult heights land inside the range the app shows. So we do not know, and we do not claim, how likely it is to be right. You will never see an accuracy percentage or a "chance" of reaching a height in Tallmark, because we cannot honestly give one.
Your adult height may be taller or shorter than the range.
It is not a diagnosis, a medical assessment or a guarantee.
Why it can be off
Your parents' heights. If they were guessed or remembered rather than measured, the estimate can move by several centimetres.
Puberty answers. Rating your own puberty is useful but rough, and everyone's timing is different.
Measuring. Your height changes by about half a centimetre over a day (you are tallest just after getting up). Measuring in a different way or at a different time can look like growing or shrinking when nothing has changed.
The methods. The main method (Khamis-Roche) was developed with white American children and has only been checked for ages 4 to 17½. It was not designed for everyone Tallmark is used by.
Health and life. Illness, some medicines, and conditions that affect growth are not something the app can know about or allow for.
The methods
Khamis-Roche. What it does: Estimates adult height from current height, weight, age and parents' average height, without an X-ray. Source: Khamis & Roche, Pediatrics 1994, with the 1995 correction.
CDC 2000 growth charts. What it does: Works out your height percentile for your age and sex, and how tall someone who stays on that percentile ends up. Source: US Centers for Disease Control and Prevention, 2000.
Mid-parental (target) height. What it does: Your parents' average height, adjusted for sex, shown as the "genetic target". Source: Tanner and colleagues, 1970.
Puberty and maturity. What it does: Estimates how far through growing you might be from your puberty answers, age and height. Source: Pubertal Development Scale (Petersen 1988); Moore 2015.
The app blends these. Full references are on Health information sources (https://sites.google.com/view/tallmark/health-source).
The estimate goes with a measurement
Each estimate is worked out from a particular height measurement, and the app shows its date. If you have not measured for a while, the estimate is about you then, not today.
3. "Taller than N% of teens your age"
This line compares one measurement with the CDC 2000 growth charts, a reference made from measurements of children in the United States.
It is a population comparison, not a score, a target or a judgement. Every percentile from the 1st to the 99th is a normal height for someone.
It says nothing about how healthy you are or how tall you will end up.
It uses a US reference. People in other countries, and from different family backgrounds, can have different typical heights.
It is worked out for your age on the day you measured.
4. Nothing here makes you taller
We want to be completely clear about this, because a lot of the internet is not.
No exercise, stretch, hanging routine, food, drink, supplement, amount of sleep or posture habit makes bones longer or adds centimetres to your adult height. Once your growth plates close at the end of puberty, nothing lengthens bone.
Getting enough sleep, food and activity supports the growing you already have coming. It does not add extra on top.
Standing up straight changes how tall you measure by millimetres, and hanging from a bar can briefly undo some of the half-centimetre you lose during the day. Both disappear within hours. Neither changes your adult height.
In studies of teenagers who were already eating enough, extra milk, calcium or vitamin D did not make them taller.
Tallmark's streaks, XP and badges reward showing up, never a change in your body. Nothing in the app takes credit for growth.
Anything sold as a "height pill" or a way to "grow taller" is selling you nothing. Talk to a doctor before taking any supplement.
5. The trackers
Height. What it does: Records dated measurements and draws them on a chart, with a projected range. What it deliberately does not do: Celebrate, grade or comment on a measurement.
Weight. What it does: Records dated weights, because one estimate method uses weight. What it deliberately does not do: No BMI, no goal, no "healthy range", no opinion about going up or down.
Meals. What it does: Records what you ate, with optional nutrient amounts, and shows protein against a reference for your age. What it deliberately does not do: Grade meals, call food good or bad, set a calorie target. Calories are hidden unless you turn them on.
Movement. What it does: Records routines and activities, and compares your week with the WHO guidance of an average 60 minutes a day for 5–17-year-olds. What it deliberately does not do: Count calories burned, or treat a quiet day as a failure.
Sleep. What it does: Records nights, and shows the 8–10 hour guidance for ages 13–18 behind your bars. What it deliberately does not do: Colour short nights red or blame you for them.
Water. What it does: Records drinks against a goal you choose. What it deliberately does not do: Tell you how much you must drink. The default goal is a round number, not a medical recommendation.
Mood. What it does: Records a face and an optional note. What it deliberately does not do: Score, average, streak or compare moods, or diagnose anything.
The sleep, activity and nutrient figures are general guidance for large groups of people, from sources listed on Health information sources (https://sites.google.com/view/tallmark/health-source). They are not personal prescriptions. Your own needs may be different, especially if you have a health condition, play a lot of sport, or are recovering from illness or injury.
6. Exercises
The Train tab shows exercises with drawn demonstrations and written cues.
Stop straight away if anything hurts, and do not carry on through pain.
Warm up first, move with control, and choose the easier version if a move feels too hard.
If you have an injury, a heart or breathing condition, a joint problem, or have been told by a doctor to avoid certain activity, ask a health professional before starting.
A demonstration is a drawing. It cannot see you or check your form.
7. When to see a doctor
Most differences in height and timing are normal. People grow at different speeds and at different ages. But it is worth talking to a doctor or school nurse if:
your height has not changed at all for six months or more while you would expect to still be growing, or you are growing much more slowly than you were before (on a growth chart, dropping to a lower line);
you are much shorter or much taller than your family's heights would suggest, or than almost everyone your age;
for girls, breasts have not started to develop by 13, or periods have not started by 15 or within about three years of breasts starting to develop; for boys, the testicles have not started to get bigger by 14. Starting later than friends is common and often runs in families, so a check-up is usually reassuring;
you have lost weight without meaning to, are often very tired, or often feel unwell;
you are worried about eating, your weight, or how your body looks;
you often feel low, anxious or not yourself, or find it hard to sleep;
exercise causes pain, swelling, chest pain, fainting or breathlessness that is not normal for you.
A doctor can measure you properly, look at your growth over time and, if needed, arrange tests that no app can do. Taking a parent, guardian or trusted adult with you can help.
8. If you need help now
Tallmark is not a crisis service. If you are in danger, might hurt yourself, or someone else is in danger, call your local emergency number now, or go to the nearest emergency department.
The Coach and Tally have a few safety answers for when someone mentions self-harm, suicide, feeling unsafe, an eating disorder, pain or medicine — recognised by those words, not by anything subtler. They point you to real people who can help. They are not a replacement for them.
In Chat with Tally, questions like these are recognised on your phone and get the same reviewed safety answer, with helplines for your country. They are not sent to the AI. If the phone does not recognise one and it does reach the AI, the AI is told to answer briefly, point you to a doctor or a trusted adult and to Where to get help, and never to diagnose or say it is nothing — but an AI is not a crisis service either, and it can get this wrong. If you are in danger, do not wait for an answer in the app: call your local emergency number.
Helplines by country: If you need help now (https://sites.google.com/view/tallmark/safety-resources).
9. Accuracy of information
We have tried to base every health statement in Tallmark on reliable, published sources, and to say plainly where evidence is missing. The answers in Chat with Tally are written by an AI model as you ask, not by us, so they have not been reviewed one by one. We tell the AI to follow the same rules as the rest of the app, but it can still be wrong — see the Terms of Use (https://sites.google.com/view/tallmark/terms-of-use) section 10A. Science changes, and mistakes happen. If you think something in the app is wrong, please tell us at tallmark.support@newversion.studio.
10. Contact
New Version Ltd, New Zealand
tallmark.support@newversion.studio