How our height calculators work

Every calculator on this site runs in your browser with public, documented methods. This page explains exactly what they compute, so you can judge the results yourself.

The data: CDC growth charts

We use the CDC 2000 stature-for-age growth charts for boys and girls aged 2 to 20, the reference used by US pediatricians. For each sex and each month of age, the CDC publishes three parameters (L, M and S) that describe the full distribution of heights. M is the median height.

Height percentile

For a height X at a given age and sex, the z-score is z = ((X / M)^L − 1) / (L × S), and the percentile is the share of a normal distribution below z. The 50th percentile is the median; the 3rd to 97th percentiles cover 94% of children. This is the same calculation the CDC describes for its charts. Adults (20+) are compared with the CDC curve at age 20.

Growth-curve projection

Children tend to follow their percentile line. The simplest prediction keeps your z-score and reads the height at age 20 on the same curve. It works well in childhood and near the end of growth, and least well during puberty, because early bloomers temporarily rise above their line and late bloomers drop below it.

Mid-parental target height

The genetic target (Tanner method) is the average of both parents’ heights plus 13 cm (about 5 in) for a boy, or minus 13 cm for a girl. Most children end up within about ±8.5 cm (3.3 in) of this target.

How the height calculator combines them

When both parents’ heights are given, the prediction is a weighted average of the growth-curve projection and the mid-parental target. The weight on the child’s own curve increases with age, because current height tells more about adult height as growth nears its end:

The prediction is never lower than the current height. In the “How tall will I be?” quiz, if you are in the usual puberty age range and say your growth spurt started earlier (or later) than your friends’, we move the growth-curve projection down (or up) by 2 cm.

The likely range

We show a range around each prediction: about ±7 cm (±2.75 in) in childhood, up to ±7.5 cm (3 in) for boys in early puberty, narrowing to about ±1 cm near the end of growth (16+ for boys, 15+ for girls). It is a little narrower when both parents’ heights are known. Real outcomes can fall outside it, especially for children with very early or very late puberty.

“Am I done growing?” estimate

This quiz starts from the height prediction above, then adjusts the growth left using your growth over the last 12 months (if given) and puberty signs: for boys voice, facial and body hair, and shoe size; for girls time since the first period. Little growth in the past year and advanced signs reduce the estimate; few signs at an older age suggest a late bloomer with more growth left. It is a rule-of-thumb summary of these signs, not a diagnosis.

Limits

• The CDC charts describe US children; average heights differ between countries and populations.
• The methods assume healthy growth. They don’t apply to children with conditions that affect growth.
• Puberty timing is the largest source of error between about 10 and 15.
• The clinical reference for remaining growth is a bone-age X-ray of the hand read by a doctor. We don’t use the Khamis-Roche method: it needs weight and was developed on a specific sample, and we prefer methods whose inputs and data are fully public.

Privacy

The heights you enter are processed in your browser and are not stored by us. We only count anonymous events (for example, that a calculator was used) to improve the site.

Questions or corrections: contact@tallerapp.xyz. See also our editorial policy.