WHO Child Growth Standards

Baby Growth Percentile Calculator

Review one dated measurement from birth through the day before the second birthday. Enter weight, recumbent length, head circumference, or any combination; weight plus length also adds weight-for-length.

Results are WHO sex-specific reference comparisons for one measurement date, not diagnoses or trends. Babies born preterm may need a different chart and age basis confirmed by an appropriate healthcare professional.

Before you calculate

Confirm the actual birth date and measurement date.
Select the WHO boys or girls chart used in the baby's record.
Use infant weight and lying-down recumbent length. This page does not accept or automatically adjust standing height.
Measure maximum head circumference with a non-stretchable tape.
This calculator uses chronological age and does not automatically apply corrected age.

Enter one measurement or any combination. Weight plus recumbent length adds weight-for-length. Infant BMI is not calculated here.

For a child under 2 measured standing, the CDC WHO SAS method adds 0.7 cm to approximate recumbent length. Do not enter unadjusted standing height here or change a clinical record yourself; ask an appropriate healthcare professional how the measurement should be handled.

For a baby born preterm, the Corrected Age Calculator explains the timeline but does not decide which growth chart to use.

Sex used for the WHO chart

WHO provides separate growth standards for boys and girls. Choose the chart used in your baby's medical record.

Units

Changing units clears all measurement values.

Date of birth

Date measured

Measurements

Weight (lb) — optional

Weight (oz) — optional

Recumbent length (in) — optional

At two decimal places, the WHO weight-for-length range is approximately 17.72–43.30 in.

Head circumference (in) — optional

Enter at least one measurement. Weight plus recumbent length adds weight-for-length.

Use a lying-down recumbent length, not unadjusted standing height. Measure maximum head circumference with a non-stretchable tape. Accurate, repeatable measurements matter.

The broad maximums are technical protections against likely entry or unit errors, not infant normal ranges.

What you can calculate from the measurements you have

Each indicator has its own required measurement and comparison basis. Enter only the measurements you actually have; the calculator does not require all three.

Weight-for-age: Measurements required: Weight; Comparison basis: Same exact age and sex; Question answered: Where weight falls for age; What it does not answer: Length, weight status, or a nutrition diagnosis
Length-for-age: Measurements required: Recumbent length; Comparison basis: Same exact age and sex; Question answered: Where lying-down length falls for age; What it does not answer: Standing height, growth pace, or adult height
Weight-for-length: Measurements required: Weight and recumbent length; Comparison basis: Same sex and recumbent length; Question answered: Where weight falls at that length; What it does not answer: Age-based position, infant BMI, or a diagnosis
Head circumference-for-age: Measurements required: Maximum head circumference; Comparison basis: Same exact age and sex; Question answered: Where head circumference falls for age; What it does not answer: Brain development, neurological status, or disease

Why the four percentiles can differ

Age-based indicators and the length-based weight-for-length indicator use different coordinates and measurements. Their percentiles do not need to match, and different results do not automatically contradict one another. This page does not infer body proportionality, stunting, wasting, feeding adequacy, neurological status, or disease from a combination of results.

Need a fuller explanation? Read What Do Baby Growth Percentiles Mean?.

Measurement workflow: weight

Use a calibrated infant scale on a stable, level surface. Minimize clothing and diaper effects, center the baby, wait until the baby is as still as practical, and record the displayed value. Repeat an uncertain reading. When using US units, enter whole pounds and the remaining ounces rather than a decimal-pound estimate.

Measurement workflow: recumbent length

Use an infant length board with a fixed headboard and movable footboard, ideally with two people. Center the head against the fixed headboard, gently straighten both legs, place the feet vertically against the footboard, and record to the nearest 0.1 cm.

This calculator accepts recumbent length only. The CDC WHO SAS method adds 0.7 cm to a standing height measured before age 2 to approximate recumbent length, but this calculator does not apply that adjustment. Do not substitute unadjusted standing height or alter a clinical record yourself; an appropriate healthcare professional should decide the measurement method and handling.

Measurement workflow: head circumference

Use a narrow, non-stretchable tape above the eyebrows and around the maximum occipital circumference at the back of the head. Keep the tape level and snug, repeat the measurement, and record the largest accurate value to the nearest 0.1 cm.

One measurement is not a trend

This page describes one measurement date. One measurement does not show a growth trend; a pattern requires repeated accurate measurements. The Growth Velocity Calculator reports arithmetic change between two dated measurements, but this site does not calculate WHO infant velocity percentiles.

Term, preterm, and corrected age

This calculator uses the actual birth date and chronological age. It does not automatically apply corrected age and does not select Fenton, Olsen, or another preterm chart. The Corrected Age Calculator provides a timeline only; an appropriate healthcare professional should confirm the chart and age basis.

The age-2 handoff

This page stops on the day before the second birthday. Starting on the second birthday, use the CDC Growth Chart Calculator. The handoff generally changes recumbent length to standing height and weight-for-length to BMI-for-age screening. Because the chart and measurement method change together, a percentile can change without automatically indicating a growth problem.

Before age 2, a standing height is not interchangeable with the recumbent-length field. The CDC WHO SAS method adds 0.7 cm to standing height to approximate recumbent length; this calculator does not do so automatically. An appropriate healthcare professional should decide how to handle the measurement and the chart transition.

Screening positions without diagnosis

CDC and AAP describe the 2nd and 98th percentile lines on adapted WHO charts as screening positions for selected indicators. They are not independent diagnoses, and this page does not use them to produce disease or treatment conclusions. Accurate measurement and the pattern over time still matter.

A separate WHO/CDC technical extreme-value flag can prompt measurement review. It does not hide the percentile, label the result abnormal, or diagnose a condition.

If a result surprises you

Check the birth and measurement dates.
Check the WHO sex chart.
Check the selected units.
Repeat only the measurements that were entered.
Confirm recumbent length was measured lying down.
Compare with previous dated clinical records when available.
Discuss a persistent concern with an appropriate healthcare professional.

Worked example

A girl born January 1, 2026 and measured February 20, 2026 is 50 days old. At 5.3 kg, 57.1 cm recumbent length, and 37.6 cm head circumference, the results are about the 76th percentile for weight-for-age, the 72nd percentile for length-for-age, the 65th percentile for weight-for-length, and the 46th percentile for head circumference-for-age.

Each indicator answers a different question; higher is not better, one measurement is not a trend, and the example is not a target.

How calculations work

The calculator uses the actual birth date, measurement date, chronological age, and WHO sex-specific standards. Weight-for-age, length-for-age, and head circumference-for-age use exact age in days. Weight-for-length is indexed by recumbent length and does not use age as its chart axis.

Weight-for-age and weight-for-length use the WHO adjusted-z method where applicable; length-for-age and head circumference-for-age use the base LMS result. For a weight-for-length input between formal 0.1 cm rows, the calculator first interpolates L, M, and S, then calculates one adjusted z-score without rounding intermediate values. Detailed formulas, z-scores, and interpolation information remain in the calculation details. Read the Methodology for the technical implementation and data-license record.

Limitations

Results depend on accurate dates, units, sex chart, and carefully repeated measurements.
The reference is for the term birth-to-before-age-2 workflow; preterm assessment may require another chart and age basis.
The calculator uses chronological age and does not automatically apply corrected age or select a preterm chart.
It accepts recumbent length only and does not add the CDC WHO SAS 0.7 cm adjustment to a standing height; do not enter an unadjusted standing value.
It does not calculate infant BMI or a WHO infant velocity percentile.
One result is not a trend, diagnosis, treatment recommendation, or complete health assessment.

Sources

1
WHO — Child Growth Standards
2
WHO — Weight-for-age
3
WHO — Length/height-for-age
4
WHO — Weight-for-length/height
5
WHO — Head circumference-for-age
6
WHO — Software and LMS resources
7
CDC — Recommended growth charts
8
CDC — Using WHO Growth Standard Charts
9
CDC — SAS Program for WHO Growth Charts
10
AAP — Term Infant Growth Tools
11
AAP — Anthropometric Measurements
12
AAP — Preterm Infant Growth Tools
13
AAP HealthyChildren — Parent guide to growth percentiles
14
WHO Child Growth Standards data used under Permission Request 202609680, granted 2026-07-16.

No WHO logo is used. Child Growth Lab is independent and is not affiliated with or endorsed by WHO. WHO data remain within the permitted website/software calculator.

Helpful context

Frequently asked questions

Which measurements can I enter?

You may enter weight, recumbent length, head circumference, or any combination. Weight-for-length appears only when both weight and recumbent length are available.

What is the difference between weight-for-age and weight-for-length?

Weight-for-age compares weight with babies of the same age and sex but does not account for length. Weight-for-length compares weight with babies of the same sex at the same recumbent length and is not infant BMI.

Why is weight-for-length missing?

Weight-for-length requires both weight and recumbent length, and the submitted length must fall within the WHO source table range of 45.0 to 110.0 cm. Other available results can still be calculated.

Is infant BMI calculated?

No. This calculator reports weight-for-length when weight and recumbent length are available. CDC does not recommend BMI-for-age interpretation for children younger than 2 years.

Does feeding type change which WHO chart is used?

No separate chart is selected by feeding type. WHO standards are used for both boys and girls, while feeding history can still be relevant when a healthcare professional interprets the growth pattern.

Should I enter recumbent length or standing height?

Enter only recumbent length measured lying down. The CDC WHO SAS method adds 0.7 cm to standing height measured before age 2 to approximate recumbent length, but this calculator does not make that adjustment. Do not enter unadjusted standing height or change a clinical record yourself; an appropriate healthcare professional should decide how to handle it.

Does the calculator use corrected age?

This calculator uses chronological age from the actual birth date. It does not apply corrected age or select a preterm growth chart. Ask the baby’s healthcare professional which chart and age basis should be used.

What happens at the second birthday?

This WHO calculator stops on the day before the second birthday. From the second birthday onward, use the CDC growth calculators and standing-height measurement approach when appropriate.

Does this site save the measurements?

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