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CDC Length-for-Age Growth Chart (0-36 Months)

Plot your child's recumbent length against CDC reference data for ages 0-36 months. The chart displays standard percentile curves with your child's measurement highlighted.

LMS Method: Z = ((X/M)^L - 1) / (L x S)

How It Works

This calculator uses CDC growth reference data for monitoring length in children from birth to 36 months. Length-for-age percentiles help assess whether your child's recumbent length is within the expected range for their age and sex. The calculator applies the LMS method (Lambda-Mu-Sigma), a statistical technique that models the distribution of length at each age. Lambda (L) accounts for skewness, Mu (M) is the median, and Sigma (S) is the coefficient of variation.

Example Problem

A newborn boy measures 49.99 cm in recumbent length. What is his length-for-age percentile?

  1. Enter the child's date of birth and measurement date (same day for a newborn).
  2. Select 'Boy' for gender.
  3. Enter 49.99 cm for length.
  4. The calculator finds the LMS parameters for boys at birth and computes the Z-score.
  5. Result: approximately the 50th percentile, since 49.99 cm is the CDC median length for boys at birth.

Key Concepts

A length-for-age percentile indicates the percentage of children who are shorter than your child at the same age. The 3rd to 97th percentile range is considered normal. Below the 3rd may indicate short stature, and above the 97th may indicate tall stature. For children under 2 years, recumbent length (measured lying down) should be used. Standing height is about 0.7 cm shorter than recumbent length. The CDC recommends WHO charts for children under 2, but CDC 0-36 month charts remain widely used.

Applications

  • Well-child visits to monitor linear growth
  • Identifying potential growth disorders early
  • Tracking catch-up growth in premature infants
  • Assessing nutritional adequacy during infancy
  • Evaluating growth in children with chronic conditions

Common Mistakes

  • Measuring standing height instead of recumbent length for children under 2 — standing height is about 0.7 cm shorter
  • Using the wrong chart for the child's age — this chart covers 0-36 months; use CDC 2-20 stature-for-age for older children
  • Not accounting for prematurity — premature infants should use corrected age for the first 2-3 years
  • Focusing on a single measurement rather than the growth trend over multiple visits
  • Comparing length measured at home (often inaccurate) with clinical measurements

Frequently Asked Questions

What age range does this calculator cover?

This calculator uses CDC growth reference data for children from birth to 35.5 months. The CDC data uses half-month intervals for precise tracking during rapid growth.

Should I measure length or height?

For children under 2 years, use recumbent length (measured lying down). For children 2 years and older, standing height is typically used. Standing height is about 0.7 cm shorter than recumbent length.

How is this different from the WHO calculator?

The WHO growth standards describe optimal growth based on breastfed children from multiple countries. The CDC charts describe how U.S. children actually grew, including both breastfed and formula-fed infants.

Reference: CDC Growth Charts: United States. National Center for Health Statistics, 2000. https://www.cdc.gov/growthcharts/

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