Calendar age is not enough
Maturation expresses how biologically mature a child is. Calendar age (how old they are) and biological age (how far their body has developed) often do not match. Two children with the same birthday can differ by as much as 2–4 years in maturity: one may develop early and enter the growth spurt before peers, while another develops late and at the same age still shows a childlike developmental profile. Both of these differences are entirely normal.
This is exactly why assessing growth, sport and height prediction by calendar age alone is misleading. The level of maturation usually explains where a child is and where they are heading far better than calendar age.
How is maturation assessed?
There are several ways to estimate maturation. Bone age (a hand-wrist X-ray) is the gold standard of skeletal maturation; it can be ahead of or behind calendar age. Tanner stage classifies pubertal development into 5 stages based on secondary sex characteristics. The percentage of predicted adult height (%PAH) shows what percentage of their eventual adult height a child has currently reached, offering a practical, radiation-free indicator of maturity.
Each of these methods looks through a different window, but all answer the same question: where is this child in their growth journey? The platform helps estimate maturation without an X-ray by calculating indicators such as %PAH from height and parental data.
Why does it matter so much?
Maturation is especially critical in sport. An early developer may be mistaken for “talented” because they are temporarily taller, stronger and faster; yet this advantage is often not skill but a difference in maturity. Late-developing but genuinely talented children, on the other hand, may be cut because they are physically overpowered. Taking maturation into account prevents this misjudgement and ensures fair assessment (see bio-banding, relative age effect).
It is also decisive for injury: the growth-spurt period (circa-PHV) is a window of increased injury risk; adjusting training load according to maturation is important for safety. In height prediction, maturation directly affects the estimate because it determines the amount of “remaining growth”.
Developing early or late
Developing early or late is not in itself a problem; it is often a familial pattern. An early-developing child grows before peers but their growth plates may also close earlier; a late-developing child looks short for a long time but has a longer period of growth and often catches up with peers later.
What matters is recognising the child’s own pace of maturation and setting expectations accordingly. If the pace of maturation is at the extreme ends (very early or very late puberty), this is a situation that also needs separate evaluation (see precocious puberty, delayed puberty).
What it means in practice for families
The concept of maturation helps families adopt a healthier perspective when comparing their children with others. Comparisons such as “their peer is taller” or “their friend is stronger” often reflect not a real difference but only a difference in the pace of maturation. Developing early or late is not a race; every child has their own timetable, and this timetable is largely determined familially.
This perspective helps keep expectations realistic, especially in sport and at school. Rather than seeing a late-developing child as “behind”, it is important to remember that they simply have not had their own spurt yet; and not to mistake an early-developing child’s temporary advantage for a permanent talent. Understanding maturation protects both the child’s confidence and makes it possible to support their development in the right way at the right time.