InfantChart
Share:

CDC Weight-for-Age Growth Chart (2-20 Years)

Plot your child's weight against CDC reference data for ages 2-20 years. 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 weight in children and adolescents aged 2 to 20 years. The CDC 2-20 year charts are the standard recommended by the CDC for this age range in the United States. The LMS method computes Z-scores and percentiles by comparing your child's weight to age- and sex-specific reference values derived from U.S. national health surveys.

Example Problem

An 8-year-old boy weighs 25.8 kg. What is his weight-for-age percentile?

  1. Enter the child's date of birth and measurement date (8 years apart).
  2. Select 'Boy' for gender.
  3. Enter 25.8 kg for weight.
  4. The calculator finds the LMS parameters for boys at age 8 and computes the Z-score.
  5. Result: approximately the 50th percentile, as 25.8 kg is near the CDC median weight for boys at age 8.

Key Concepts

Weight-for-age in the 2-20 year range should be interpreted alongside height and BMI. A child may be heavy for their age but appropriately proportioned for their height. During puberty, weight gain accelerates due to both muscle and fat changes. Persistent tracking below the 3rd percentile may indicate failure to thrive or a chronic condition, while tracking above the 97th may warrant obesity screening.

Applications

  • Routine growth monitoring at well-child visits
  • Screening for underweight or overweight in school-age children
  • Monitoring weight during puberty and adolescence
  • Tracking weight in children with chronic illness or medication effects
  • Nutritional counseling and dietary assessment

Common Mistakes

  • Using weight-for-age alone to diagnose obesity — BMI-for-age is the recommended screening tool for children over 2
  • Using the CDC 0-36 month chart for children over 3 years
  • Not considering pubertal development when interpreting weight changes
  • Confusing percentile with percentage — the 85th percentile does not mean the child is 85% of a healthy weight
  • Not accounting for unit conversion between kg and lb

Frequently Asked Questions

What age range does this calculator cover?

This calculator uses CDC growth reference data for children and adolescents aged 2 to 20 years. For children under 2, use the CDC 0-36 month weight-for-age chart.

Should I use my child’s weight in kg or pounds?

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

How is this different from the WHO calculators?

The WHO provides growth standards for children under 5 and references for ages 5-19. The CDC 2-20 charts are based on U.S. population data and are the standard recommended by the CDC for children aged 2 and older in the United States.

Are these the same charts my doctor uses?

Yes, the CDC 2-20 year growth charts are the most commonly used charts in U.S. pediatric practices for children aged 2 and older. They are recommended by the CDC for routine growth monitoring.

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

Related Calculators

Related Sites