Child Weight Percentile Calculator

Use one dated weight measurement from the second birthday through the day before the 20th birthday to calculate its CDC weight-for-age reference position.

Weight-for-age does not account for height, produce BMI or a weight-status category, or diagnose nutrition or health. For a child under 2, use the WHO Baby Growth Percentile Calculator.

Before you calculate

Confirm the actual birth date and measurement date.
Select the CDC boys or girls chart used in the child’s record.
Use a digital scale on firm, level flooring.
Remove shoes and heavy clothing.
Have the child stand with both feet centered and remain still.
Record the nearest decimal fraction shown by the scale.
Repeat an uncertain reading.
When comparing dates, use the same scale and similar conditions where practical.
This calculator uses the actual birth date and measurement date to calculate calendar age. It does not automatically apply corrected age, so do not change the actual birth date or substitute corrected age as the CDC weight-for-age input age. For a child with a history of preterm birth, an appropriate healthcare professional should confirm the age basis and chart; this site does not automatically select a preterm chart.

Review the measurement workflow, age-2 handoff, and weight-for-age versus BMI. With one weight, stay here. With same-date height, use the Kids BMI Calculator or Child Growth Chart Calculator. With a second dated weight, use the Growth Velocity Calculator. Before age 2, use the Baby Growth Percentile Calculator.

Sex used for the CDC chart

CDC provides separate weight charts for boys and girls. Choose the chart used in your child’s medical records.

Units

Changing units clears the weight field.

Date of birth

Date measured

Weight (lb)

Use a digital scale on firm, level flooring. Remove shoes and heavy clothing, stand with both feet centered, remain still, and record the nearest decimal fraction shown by the scale.

What this calculator answers

One dated weight record produces one CDC weight-for-age reference position for the child’s exact age and selected sex chart. It does not adjust for height or explain BMI, weight status, body composition, nutrition status, or why a measurement changed.

Need a fuller explanation of the number? Read What Does a Child’s Weight Percentile Mean?

Measurement workflow

Place a digital scale on firm, level flooring.
Zero or reset the scale if required by its instructions.
Remove shoes and heavy clothing.
Have the child stand with both feet centered and remain still.
Record the nearest decimal fraction shown by the scale.
Repeat an uncertain reading.
When comparing dates, use the same scale and similar conditions where practical.

Why exact dates and chart selection matter

The same weight can occupy a different reference position at a different age. This calculator uses the actual birth date and measurement date instead of a rounded age. CDC provides separate boys and girls weight-for-age references; select the chart used in the child’s medical record.

Weight-for-age, BMI-for-age, change over time, and combined review are different questions

Current weight-for-age: Measurements: One dated weight; Use: This calculator; Output: Does not account for height
Weight relative to height: Measurements: Same-date height and weight; Use: Kids BMI Calculator; Output: BMI-for-age and CDC screening category
Change over time: Measurements: Two dated weights; Use: Growth Velocity Calculator; Output: Arithmetic change rate, not a CDC velocity percentile
Combined current review: Measurements: Same-date height and weight; Use: Child Growth Chart Calculator; Output: Height, weight, BMI, and how the results differ

The age-2 handoff

Before the second birthday, use the WHO Baby Growth Percentile Calculator. That tool can distinguish weight-for-age from weight-for-length. This CDC calculator begins on the second birthday as calculated from the actual birth date and measurement date. It does not automatically apply corrected age, corrected age must not be substituted as the CDC weight-for-age input age, and the actual birth date must not be changed. For a child with a history of preterm birth, an appropriate healthcare professional should confirm the age basis and chart; this site does not automatically select a preterm chart.

One point is not a trend

This page describes one measurement date. It cannot calculate change or growth velocity. With a second dated weight, use the Growth Velocity Calculator; it reports arithmetic change and does not automatically explain a cause or diagnose a condition.

If the result surprises you

Check the birth date.
Check the measurement date.
Check the CDC chart selection.
Check kg versus lb.
Confirm the scale is on a firm, level surface.
Repeat the measurement under consistent conditions.
Compare with prior dated clinical records when available.
Discuss a persistent concern with an appropriate healthcare professional.

Worked example

A boy born October 1, 2007 and measured on November 15, 2011 is 4 years, 1 month, 14 days old. At 16.9 kg, the result is about the 58th percentile on the male CDC weight-for-age chart.

This is a weight-for-age reference position. It does not account for height, assign a BMI category, define a target or normal range, or establish a trend from one record.

How the calculation works

Exact elapsed age selects the sex-specific CDC weight-for-age LMS reference. The calculator interpolates between the appropriate CDC age anchors, applies the LMS formula, and converts the z-score to a percentile. The collapsed result details retain source, anchor, z-score, and technical measurement-review information. See the Methodology.

Limitations

The result uses one weight measurement and does not adjust for height.
It does not provide a BMI category, body-composition estimate, nutrition diagnosis, growth trend, or cause attribution.
It does not provide treatment or diet advice.
Measurement conditions, accurate dates, units, and correct chart selection affect the result.
The calculator uses the actual birth date and measurement date to calculate calendar age. It does not automatically apply corrected age or select a preterm chart; do not change the actual birth date or substitute corrected age as the CDC input age. An appropriate healthcare professional should confirm the age basis and chart for a child with a history of preterm birth.
It is not for children under 2 and is not a diagnosis.

References

Helpful context

Frequently asked questions

What information do I need?

You need the child’s birth date, the weight measurement date, the CDC boys or girls chart used in the child’s record, the submitted unit, and one weight measurement.

Why are exact dates required?

CDC weight-for-age references change with age. Exact birth and measurement dates allow the calculator to use exact elapsed age instead of a rounded age estimate.

How should weight be measured?

Use a digital scale on firm, level flooring. Remove shoes and heavy clothing, have the child stand with both feet centered and remain still, and record the nearest decimal fraction shown by the scale. Repeat an uncertain reading. When comparing dates, use the same scale and similar conditions where practical.

Why did the result change after remeasuring?

Scale position, units, clothing, and measurement conditions can change a reading. Repeat an uncertain measurement under consistent conditions and use the carefully recorded value.

Does weight percentile classify underweight or overweight?

No. Weight-for-age does not account for height and is not used to classify underweight, healthy weight, overweight, or obesity. BMI-for-age is the CDC weight-status screening index.

What should I use when I also have height?

Use the Kids BMI Calculator for BMI-for-age and a CDC screening category, or the Child Growth Chart Calculator to review same-date height, weight, and BMI together.

What should I use when I have two weight measurements?

Use the Growth Velocity Calculator to calculate arithmetic weight change between two dated measurements. It does not provide a CDC growth-velocity percentile or diagnose a cause.

What should I use for a child under 2?

Use the WHO Baby Growth Percentile Calculator before the second birthday based on the actual birth date. Do not change the birth date or substitute corrected age as the input age for this CDC calculator. For a child with a history of preterm birth, an appropriate healthcare professional should confirm the age basis and chart; this site does not automatically select a preterm chart.

Does this site save the weight measurement?

Calculator inputs are processed in your browser and are not saved as a child health record or sent to an external calculation service.