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How Stature-for-Age Percentiles Work (2-20 Years)

This calculator uses CDC growth reference data for children and adolescents ages 2 to 20 years. Stature (standing height) is measured with the child standing upright against a stadiometer. The CDC growth charts help assess whether a child’s height is within the normal range for their age and sex.

The calculator uses the LMS method (Lambda-Mu-Sigma), a statistical technique that summarizes the distribution of stature at each age using three parameters. Lambda (L) accounts for the skewness of the distribution, Mu (M) is the median, and Sigma (S) is the coefficient of variation.

Understanding Height Percentiles

A percentile indicates the percentage of children who are shorter than your child. For example, if your child is at the 75th percentile, 75% of children of the same age and sex are shorter.

  • 3rd to 97th percentile is considered the normal range
  • Below the 3rd percentile may indicate short stature
  • Above the 97th percentile may indicate tall stature
  • The growth velocity (rate of change) is as important as the absolute percentile

Example Calculation

A 10-year-old boy (120 months) measuring 139.73 cm would be approximately at the 50th percentile (Z-score near 0), since the CDC median stature for boys at 120 months is about 139.73 cm.

Frequently Asked Questions

What age range does this calculator cover?

This calculator uses CDC growth charts for children and adolescents from 2 to 20 years (24 to 240 months). For children under 2 years, use our length-for-age calculator (measured lying down).

Should I use my child’s height in cm or inches?

You can use either unit. The calculator converts inches to centimeters automatically. For the most accurate result, use the height recorded at your pediatrician’s office.

What is the difference between stature and length?

Stature is standing height, measured with the child upright. Length is recumbent length, measured lying down. For children under 2, length is used. For children 2 and older, standing height (stature) is used. Standing height is typically about 0.7 cm shorter than recumbent length.

When should I be concerned about my child’s height?

Consult your pediatrician if your child falls below the 3rd percentile, above the 97th percentile, or if there is a significant change in growth trajectory (crossing two or more percentile lines over time).

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