Height percentile calculator
Where a child's height sits against others of the same age and sex, computed from the parameters the CDC growth charts are built from rather than read off a printed curve.
Boy, 8 years 0 months, 130.0 cm
64.3th percentile
Taller than about 64 in every 100 children of that age and sex. The z-score is 0.37, meaning 0.37 standard deviations above the median of 127.9 cm.
The chart lines at this age
- 3th percentile
- 117.3 cm46.2 in
- 10th percentile
- 120.6 cm47.5 in
- 25th percentile
- 124.0 cm48.8 in
- 50th percentile
- 127.9 cm50.3 in
- 75th percentile
- 131.8 cm51.9 in
- 90th percentile
- 135.4 cm53.3 in
- 97th percentile
- 139.0 cm54.7 in
How it is worked out
The charts publish three numbers for every age and sex: L, the power of the Box-Cox transformation; M, the median; and S, the coefficient of variation. A height becomes a z-score with z = ((height ÷ M)L − 1) ÷ (L × S), and the percentile is the normal distribution evaluated at that z. Reading a percentile off a printed curve approximates this; the arithmetic here is the thing the curve was drawn from.
What a percentile is not
It is a position in a population, not a verdict. A child on the 10th percentile who has been on the 10th percentile all along is growing normally; a child who was on the 75th and is now on the 25th has changed track, and that is the thing worth asking a clinician about. The number here answers where, never whether.
Source: CDC 2000 Growth Charts, stature-for-age, 2 to 20 years (statage). CDC percentile data files. Not medical advice.