A clear method, with clear limits

Three different kinds of information

Recorded data

Height, the date it was measured, and family heights you choose to enter are recorded data. They describe what was measured or provided. They are not a prediction.

Calculated reference metrics

A height percentile and a z-score are calculated from recorded height, age, and sex, using WHO 2007 height-for-age reference data. They compare one measurement with a reference population. Height percentile explains that comparison in everyday language.

Priorities

The 3 priorities and the Full Personalized Plan are practical suggestions. They are not medical treatment, and they are not a guaranteed change in height.

Height percentile

Percentile answers a comparison question: among the WHO reference for the same age and sex, where does this recorded height sit? The 50th percentile is the median. Someone at the 25th percentile is shorter than about three quarters of that reference, and someone at the 75th is shorter than about one quarter of it. None of those numbers is a score.

Z-score

A z-score is the same comparison, written as distance from the median. Zero is the median. A positive number is above it, and a negative number is below it. For WHO height-for-age, the Box-Cox power L is 1, so the z-score is (recorded height − median) ÷ (median × S). S is the coefficient of variation in the published table.

Growth trajectory

Trajectory is the shape made by more than one recorded measurement. One point is a location. Several points show recorded change. The growth charts on this website show reference curves, not a personal trajectory.

Measured growth pace

Growth pace is how recorded height changed between measurements. It uses the heights and dates you entered. It does not estimate how much growth is still ahead. Growth velocity explains why the time between the two measurements is part of the result.

Family height context

Family height context places a recorded height next to family height information you add. It is context for reading the measurement. It is not a formula for adult height. Family height and growth is the longer explanation of that limit.

Growth charts

A growth chart draws reference curves of height against age. A recorded measurement can be thought about against those curves. The chart itself is a picture of the reference, not a diagnosis. See the WHO curves.

WHO reference data

Growth Predictor uses WHO 2007 height-for-age reference data for ages 5–19. The published tables list L, M, and S for each month from 61 through 228 months, separately for boys and girls. Age is completed calendar months. The measurement month counts only once its day reaches the birthday day, and that month selects one published row with no interpolation. Ages outside 61 through 228 months are not calculated.

WHO reference data does not predict an individual’s final adult height. It describes how height was distributed in the reference at each age.

Why repeated measurements matter

Repeating a measurement shows change that one reading cannot. It also makes it easier to notice a reading that was taken differently from the others.

Measurement variation

Standing height can differ slightly from morning to evening, and from one technique to another. Shoes, hair, posture, and an uneven floor all change the number. A consistent method makes the recorded series easier to read.

Limitations

The reference starts at 61 months and ends at 228 months. Outside that range, this method does not produce a percentile. The tables are sex-specific as published by WHO. A percentile cannot see nutrition, health, puberty, or measurement error unless those things have already affected the recorded height.

What Growth Predictor does not calculate

• Guaranteed adult height
• Exact future height
• Centimeters left to grow
• A medical diagnosis
• Treatment recommendations

It also does not recommend supplements or hormones to increase height, and it does not promise that a lifestyle change will add centimeters.

If a growth pattern is worrying, a qualified healthcare professional can interpret it in person. A chart or a percentile cannot do that alone.