What is a pediatric growth chart calculator?

A pediatric growth chart calculator compares a child’s measurements (such as weight, length/height, head circumference, or BMI) with reference data from large populations (WHO or CDC). It returns a percentile and z-score that show how the child’s growth compares with other children of the same age and sex.

Which growth standards does this tool use?

This tool is designed around WHO Child Growth Standards for ages 0–5 years and CDC growth references for ages 2–20 years. The demo implementation uses an internal reference table and z-score formulas to approximate percentiles. For clinical decisions, always cross-check with official WHO or CDC charts.

What percentile is considered normal growth?

Most children between the 3rd and 97th percentile are considered within the normal range, provided their growth curve is smooth and consistent over time. A single low or high percentile is less important than the overall pattern. Only a health professional can interpret growth in the context of the child’s history and examination.

When should I worry about my child’s growth?

Red flags include: measurements below the 3rd or above the 97th percentile, a sudden drop or jump across two or more major percentile lines, weight falling while height remains stable, or head circumference changing abruptly. If you see these patterns, discuss them with your pediatrician rather than relying on an online calculator alone.

Can I use this calculator to diagnose growth problems?

No. This calculator is for education and tracking only. It cannot diagnose growth hormone deficiency, failure to thrive, obesity, or any medical condition. Always consult a qualified health professional for diagnosis and treatment decisions.

Pediatric Growth Chart Calculator

Estimate a child’s growth percentiles and z-scores for weight, length/height, head circumference, and BMI using WHO/CDC-style charts.

Clinical disclaimer: This tool is for educational and tracking purposes only and does not replace professional medical judgment. Always confirm results with official WHO/CDC charts and consult a pediatrician for diagnosis or treatment.

Child data

Sex

Age

Years

Months

Days (optional)

Age range supported: birth to 20 years.

Measurements

Weight

Unit

Typical ranges:

Newborn: 2.5–4.5 kg
1 year: 7–12 kg

Chart type

Reference standard

We automatically switch between WHO and CDC based on age, but you can override if needed.

Results

Growth chart visualization (approximate)

This simplified chart illustrates where your child falls relative to key percentiles. For clinical use, always refer to official WHO/CDC charts.

Below 3rd 3rd 15th 50th 85th 97th Above 97th

Growth tracking table

Save multiple visits to see how your child’s growth pattern evolves over time.

#	Age	Sex	Chart	Measurement	Percentile	Z-score	Standard
No entries yet. Calculate a result and click “Add to tracking table”.

How this pediatric growth chart calculator works

Growth charts are statistical tools that compare a child’s measurements with those of many other children of the same age and sex. This calculator uses z-score–based formulas similar to those used in WHO and CDC growth standards to estimate:

Percentile (e.g., 25th, 50th, 97th)
Z-score (standard deviation score)
A brief interpretation of the result

For each chart type (weight-for-age, length/height-for-age, BMI-for-age, head circumference-for-age), the reference data provide three key parameters: the median (M), a spread parameter (S), and a skewness parameter (L). These are used in the LMS method.

The LMS z-score formula

The z-score is calculated from the child’s measurement \(X\) using:

If \(L \neq 0\):

\[ z = \frac{\left(\frac{X}{M}\right)^L - 1}{L \cdot S} \]

If \(L = 0\):

\[ z = \frac{\ln(X/M)}{S} \]

Once we have the z-score, we convert it to a percentile using the standard normal distribution. For example, \(z = 0\) corresponds to the 50th percentile, \(z = -1.88\) is about the 3rd percentile, and \(z = +1.88\) is about the 97th percentile.

WHO vs CDC growth standards

WHO Child Growth Standards: based on healthy, breastfed children from multiple countries; typically used from birth to 5 years.
CDC Growth Charts: based on US survey data; commonly used from 2 to 20 years.

This calculator’s “Auto” mode follows a common approach:

0–24 months: WHO standards
2–20 years: CDC references

Interpreting growth percentiles

Percentiles describe how a child compares with peers:

50th percentile: exactly average for age and sex.
10th percentile: smaller or lighter than 90% of peers.
90th percentile: larger or heavier than 90% of peers.

Most healthy children fall between the 3rd and 97th percentile. Being at the 5th or 95th percentile can still be normal, especially if the child has always tracked along that curve and the parents are also small or tall.

Red flags to discuss with a pediatrician

Measurements consistently below the 3rd or above the 97th percentile.
A child who crosses two or more major percentile lines (for example, from 75th to 10th percentile).
Weight dropping while height remains stable, or vice versa.
Head circumference that suddenly accelerates or decelerates.

These patterns do not automatically mean something is wrong, but they warrant a professional evaluation. Only a clinician can interpret growth in the context of medical history, nutrition, and physical examination.

Limitations of online growth chart calculators

Small differences in age calculation (e.g., rounding months) can change percentiles.
Home measurements may be less accurate than clinic measurements.
Different countries may use different reference charts or updated versions.
This tool uses an internal reference table and approximations; it is not a certified medical device.

Always use this calculator as a complement to, not a replacement for, official WHO/CDC charts and professional medical advice.