Tall or nahTall or nah logo

Tall or nah for doctors—a simple way to help families understand height percentiles.

A pediatrician examining a girl.

Tall or nah is a completely free, doctor- and patient-friendly height calculator powered by the same impressive dataset underlying the CDC (Centers for Disease Control and Prevention) Growth Charts.

Tall or nah is the only height calculator that uses population statistics to determine how tall a child is precisely for their age (measured in weeks) and biological sex.

Tall or nah is also the only height calculator that can statistically predict a child's adult height with a relatively high degree of accuracy, starting at the age of 2 years old.

How Tall or nah works

In the most technical sense, Tall or nah is an advanced statistical LMS calculator. LMS (lambda, mu, sigma) are parameters used in statistical modeling to describe the distribution of data, like height across age and biological sex. LMS is widely used in population-based statistics for its accurate percentiles and smooth curves.

LMS is the methodology that was used to model the data that is now represented by the CDC Growth Charts. So, naturally, Tall or nah was built to perform calculations on this type of data. And it was designed to be simple enough for anyone to use.

Tall or nah takes a person's height, age, and biological sex and ranks their height among their peers within the population. This rank is expressed as a percentile—the percentage of people the same age and biological sex they are taller than.

By itself, this percentile is rather interesting, because it tells the subject how tall they are for their age and biological sex strictly by comparison against their peers—tallness is never defined arbitrarily.

Tall or nah then uses this percentile to project their adult height because height percentiles tend to track consistently over time. By reverse calculating the height of adults in that same percentile, Tall or nah can, with remarkable accuracy, statistically predict the subject's adult height.

How does percentile tracking compare to the mid-parental height formula?

There is almost no comparing the two methods for accuracy.

First and foremost, the genes that determine a person's height potential could have come from anyone in their family tree, not just the parents—they could have come from a number of relatives over a number of generations.

Second, by the time a child is walking on their own, their genetic height potential has had enough time to play out for Tall or nah to begin making statistical predictions about height trajectory, with relatively high degrees of accuracy. Naturally, the older a person gets, the more accurate their prediction becomes. By the teenage years, this prediction will be exceptionally accurate.

Minimum age

Because Tall or nah is powered by CDC Growth Charts data, the minimum age Tall or nah can begin to rank height against peers and statistically predict adult height is 2 years old—giving clinicians and families a powerful, easy-to-use tool at a very early age in a child's life.

How to use Tall or nah

First, enter the patient's information into the calculator to determine their peers:

Then hit the button to see their height percentile—the percentage of their peers they're taller than. And if they're still growing, you will see their projected adult height—more technically, the median of their height potential (the middle value in their range of genetic height possibilities).

It's that easy! It's also really fun!

Accuracy

The data that powers Tall or nah is staggeringly accurate. Don't let the name fool you, what you are accessing here is, in actuality, one of the most authoritative datasets in American pediatric health.

The dataset that powers Tall or nah comes from 19 cumulative years of data collection that was funded and overseen by the National Center for Health Statistics in the United States. The study, which spanned four consecutive decades, measured the heights of tens of thousands of people across every major racial and ethnic group in America from infancy to adulthood. It was this landmark survey that produced the CDC Growth Charts.

And it is this very data that powers every Tall or nah calculation.

How Tall or nah can be useful in practice

Height Advantage

While the height calculator is the bread and butter of Tall or nah, Height Advantage: The Ultimate Guide to Unlocking Max Height is the slice of unforgettable cake.

The guide answers virtually every question a parent or patient might have about height—their own or their child’s. It is an invaluable resource for anyone interested in reaching the upper limits of their genetic height potential.

Does Tall or nah sell user data?

Absolutely not!

Tall or nah doesn't even collect data—let alone sell it. All of the data that is entered into Tall or nah is used strictly to perform height calculations. The moment you close the web browser, all of your input data is gone forever.

Tall or nah is funded entirely by family-friendly ads, just like your favorite free medical journal.

Was Tall or nah made by doctors?

The people who built Tall or nah are mathematicians, statisticians, and software engineers. We have a passion for building software that not only does powerful things but helps people—especially if it can help people for free. And we love having fun, which is why Tall or nah was designed to be a little cheeky.

For clinicians who want to learn more

The Tall or nah website is rich in literature about how the calculator works, the data that powers the calculator, statistical modeling, and more. If you want to learn more about Tall or nah and whether it's right for you or your patients, we encourage you to look around the website. We're confident all of your questions will be answered.

If you do have questions, feel free to contact us down below!

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