Child Height Predictor — how tall will my child be?

This predictor combines two independent, published methods. The first needs only the parents' heights; the second refines the estimate when you know how your child is growing right now.

1. Mid-parental (target) height

Introduced by Tanner, Goldstein and Whitehouse in 1970, the mid-parental method assumes a child's adult height clusters around the average of the two parents, shifted by the typical adult height gap between the sexes:

• Boy: (father + mother + 13) ÷ 2
• Girl: (father + mother − 13) ÷ 2

The 13 cm adjustment is the average difference between adult men and women. Because real children scatter around this target, the tool shows an expected band of about ±8.5cm (roughly ±2 standard deviations): most children finish somewhere inside it. The tool also cross-checks the result against the algebraically-equivalent “parental average ± 6.5cm” form, so you can see the two formulas agree to the millimetre.

2. WHO growth-trajectory projection

Given the child's current age (4–17.5 years) and height, the tool computes their WHO height-for-age z-score — how far above or below the median they sit today — using the WHO Growth Reference (the same standard behind the CHDR growth card). Healthy children tend to grow along a stable percentile channel, so we hold that z-score constant and read off the height at the 19-year (near-adult) reference point:

• z = (current height ÷ median-for-age − 1) ÷ S-for-age
• adult height = median​(19y) × (1 + z × S​(19y))

This second figure is personalised to how your child is actually tracking, and it is shown alongside the mid-parental estimate rather than replacing it. When both land close together you can be more confident; a wide gap simply flags that your child is currently taller or shorter than their genetic average.

A note on method choice. The proposal for this tool called for the weight-based Khamis-Roche regression. Its accuracy depends on proprietary age-and-sex coefficient tables from the 1994 paper that we could not verify against an authoritative, freely-published source. Rather than ship numbers we cannot stand behind, the current-measurement refinement uses the WHO percentile-tracking projection above, which is fully reproducible from published data. This is an estimate, not a diagnosis.

• Tanner JM, Goldstein H, Whitehouse RH — Standards for children's height allowing for height of parents (Arch Dis Child 1970;45:755–762)
• WHO — Growth Reference data for 5–19 years (height-for-age)
• WHO — Child Growth Standards (under-5 references)
• Family Health Bureau, Sri Lanka — Child Health Development Record (CHDR) context

The mid-parental correction and the WHO height-for-age LMS values used here were last cross-checked on 2026-07-09. This tool gives an estimate for information only and does not replace advice from a paediatrician or your MOH / PHM clinic.