Growth Chart Calculator: Percentiles by Age and Sex

Use the Growth Chart Calculator

Estimate length/height percentiles by age and sex and see a quick z‑score snapshot.

How to Use Growth Chart Calculator: Percentiles by Age and Sex

1. Step 1: Choose age mode

   Select months (0–24) for infants or years (2–20) for children and adolescents.

2. Step 2: Enter age

   Type age in months or years, then adjust with the slider as needed.

3. Step 3: Select sex and units

   Pick boy or girl and choose centimeters or inches. You can switch units anytime.

4. Step 4: Enter length/height

   Enter the measurement to see the estimated percentile, z‑score, and reference points.

Key Features

• Age mode: 0–24 months or 2–20 years
• WHO/CDC reference hint
• Percentile and z‑score
• Metric and Imperial units
• Mini chart export

Understanding Results

Formula

This tool estimates stature‑for‑age percentiles using a simplified approach that mirrors standard methods. For each age and sex it references a median (M) and a spread (S). A Z‑score is approximated and mapped to a percentile via the normal cumulative distribution function to provide an intuitive position on the curve.

Reference Ranges & Interpretation

Percentiles are comparison points. Many healthy children track near the same percentile line for years. As a plain‑language guide: ≤5th may be described as “below typical,” 5th–15th as “low‑average,” 15th–85th as “within typical range,” 85th–95th as “high‑average,” and ≥95th as “above typical.” Discuss sustained shifts with your clinician.

Assumptions & Limitations

The calculator uses streamlined reference curves for instant mobile results. For clinical decisions, compare with official CDC and WHO charts. Technique, equipment, and puberty timing can shift results.

Complete Guide: Growth Chart Calculator: Percentiles by Age and Sex

Use the growth chart calculator to estimate length and height percentiles by age and sex. Enter age in months or years, switch units, and see where child fits.

Why use a growth chart calculator

A growth chart calculator helps you see where a child’s length or height sits compared with peers of the same age and sex. The result is shown as a percentile. If your child is at the 60th percentile, roughly 60% of children in the reference group are shorter and 40% are taller. This is not a grade or a goal. Instead, it is a way to place a measurement in context. Parents often find the visual helpful, especially when checking progress after a growth spurt or an illness.

Our growth chart calculator focuses on clarity: you enter age, sex, and a single measurement (length for infants, height for older children). The tool estimates a z‑score and percentile using widely accepted methods, then labels the result in plain language. If you prefer to go deeper, the page also shows reference points (5th, 50th, 95th) for the same age so you can see where your number sits on the curve.

How this tool estimates percentiles

Under the hood, this tool mirrors the logic behind standard growth charts. For infants (0–24 months), it uses WHO‑like median curves for recumbent length. For children and adolescents (2–20 years), it uses CDC‑style standing height medians. Because real clinical charts use LMS parameters (L for skewness, M for median, S for variability), we use a simplified approach that closely tracks the same idea: we compare your measurement with the age‑specific median and apply a reasonable estimate of the typical spread. The resulting standard score (z‑score) converts to a percentile on the familiar 0–100 scale.

In plain English: if your child’s height is exactly the median for age and sex, the z‑score will be 0 (about the 50th percentile). Values above the median yield positive z‑scores (and higher percentiles). Values below yield negative z‑scores (and lower percentiles). The calculator also displays 5th, 50th, and 95th reference values to ground interpretation. These are not rigid pass/fail lines—they are widely used markers to describe where a measurement sits on the curve.

How to measure length/height accurately at home

Small technique differences can shift a result by a few percentiles. For infants, measure length lying flat on a firm surface. Have one adult gently hold the head in a neutral position and another extend the legs by the ankles until they are straight. Use a rigid tape or measuring board if available. Read the value at the heel to the nearest 0.1 cm (or 1/8 inch).

For older children, measure standing height without shoes. Place heels together against a wall, legs straight, arms at sides, and shoulders relaxed. Ask your child to take a deep breath and stand tall, looking straight ahead, with the back of the head touching the wall if possible. Use a right‑angle object (like a hardcover book) against the crown of the head and mark the wall lightly, then measure from floor to mark. Measure twice and average the numbers; measuring at the same time of day reduces variation.

Reading your result: percentile and z‑score

The calculator shows an estimated percentile, a z‑score, and a one‑line interpretation label. “Typical (10th–90th)” means the value sits in the broad band where most healthy children fall. Labels like “Low (5th–10th)” or “High (90th–95th)” signal a measurement near the edges, while “Below typical (<3rd)” and “Above typical (>97th)” highlight results that are more unusual in the reference group. This language is intentionally gentle: many healthy children track well below or above the 50th percentile because families come in all sizes and children mature at different times.

The z‑score is simply another way to express the same position on the curve. A z‑score near 0 is right at the median. A z‑score around +1 corresponds to roughly the 84th percentile, while −1 corresponds to the 16th percentile. Clinicians use z‑scores because they support calculations like changes across visits and comparisons across different measures (for example, comparing height‑for‑age with BMI‑for‑age).

WHO vs CDC charts (and when each applies)

In the first two years of life, many clinicians use World Health Organization (WHO) standards because they are based on a multinational sample of healthy, breastfed infants. After age two, clinicians commonly switch to Centers for Disease Control and Prevention (CDC) references, which describe U.S. population growth patterns. Our growth chart calculator defaults to WHO for 0–24 months and CDC for 2–20 years. If a clinician advises a different standard (for example, using WHO curves a bit longer), you can override the reference in the tool.

No chart is perfect. Percentiles are a guide, not a diagnosis. A child’s trend over time, family heights, medical history, nutrition, and activity all matter. Use the visual to support conversations with your pediatrician, not to replace them.

Infants vs children: length vs standing height

For 0–24 months, growth charts use recumbent length, which is measured lying down. For 2–20 years, charts use standing height. Length is typically about 0.7 cm greater than standing height in very young children because of posture and technique. Our growth chart calculator reflects this convention by asking for length in the infant mode and height in the child/adolescent mode. If you mistakenly enter a standing height in the infant mode, the result may appear slightly lower than expected.

If your child is very close to age two, you may see a small shift when you switch from length‑for‑age to height‑for‑age. That change comes from the measurement method rather than an abrupt change in the child’s body. Over the next few measurements, the new method will establish a clear trend again.

Growth velocity: why curves over time matter

Pediatric growth is a story told over months and years. A single point can be influenced by measurement technique, time of day, hydration, or a recent illness. Most clinicians focus on the curve rather than any one number. A steady track near a given band—whether that’s the 20th or the 75th percentile—often indicates expected growth. Fast stretches and plateaus happen, especially around puberty, when peers mature at different times.

If you want to track the curve at home, measure periodically using the same method and compare results in our dedicated tools. For height trends in older children, try the Child Height Percentile Calculator. For infants, see the Baby Length Percentile Calculator and the Baby Weight Percentile Calculator to track multiple dimensions together.

Common questions and quick tips

Is a higher percentile always better? Not necessarily. Healthy children grow across many different percentiles. What matters is a consistent trajectory over time that fits your child and family context. A child who tracks near the 20th percentile steadily is usually doing just as well as a child who tracks near the 70th, if health and development are otherwise typical.

What if the percentile changed a lot since last visit? First, check technique and timing. Was the child measured with shoes? Was the wall level? Did you switch from infant length to standing height? Illness, sleep, and hydration can also nudge results in the short term. If a big shift persists across two or more visits, bring it up with your pediatrician.

Can I use inches instead of centimeters? Yes. Toggle units in the tool; the math is the same. If you need a quick adult context check, see our general Height Percentile Calculator as well.

What about BMI‑for‑age? BMI‑for‑age uses weight, height, age, and sex to estimate fatness patterns during growth. To explore that dimension, try our Child BMI Percentile Calculator. You can use it alongside this page to get a more complete picture.

When to discuss results with your clinician

Percentiles are context for conversation, not a diagnosis. If a result sits far outside the usual band, or crosses major curves and stays there, or if you have concerns about nutrition, sleep, or development, ask your clinician. They will consider family heights, prior measurements, your child’s health history, and other clues that put one day’s number in perspective.

If you’re tracking an infant, your clinician may use corrected age when plotting the first months for babies born early. If you’re tracking a teen, rapid changes during puberty are common and expected. Bring your notes and any questions. Clear measurements plus your observations often speed up answers.

Helpful related calculators

You can explore growth from several angles using our other tools. If you’re tracking a baby, start with the Infant Growth Chart Calculator to view weight, length, and head size estimates together. For children over two, the Child Growth Calculator lets you save measurements to see velocity. For BMI specifically, use the Child BMI Percentile Calculator. Each page keeps the interface simple and mobile‑friendly so you can check trends during visits.

For newborn care, see the Newborn Feeding Calculator to plan feeds by age and weight alongside your pediatrician’s guidance. If you need a quick adult context later, our Height Percentile Calculator provides a broad comparison beyond childhood growth charts.

Frequently Asked Questions