Growth Percentile Calculator

Find weight, length or height and BMI percentiles on WHO and CDC growth charts from birth to 20

Child's Sex

Child's Age

years

Age Unit

Growth Chart

Child's Weight

lbs

Child's Height

inches

Results

Chart UsedCDC (2–20 years)

Weight-for-Age Percentile63rd

Height-for-Age Percentile41st

Weight-for-Age Z-Score0.34

Height-for-Age Z-Score-0.22

Child's BMI18.1

BMI-for-Age Percentile (CDC)73rd

BMI-for-Age Z-Score0.63

Weight CategoryHealthy Weight

Healthy Weight Range (5th to 85th BMI percentile)59 - 80 lbs

Weight compared with the CDC growth chart

⚠️ This calculator is for informational purposes only and should not be used as a substitute for professional medical advice. Always consult with a healthcare provider for medical concerns.

What is a Growth Percentile?

A growth percentile shows where a child's measurement falls compared with other children of the same age and sex on a growth chart. At the 60th percentile for weight, a child weighs more than 60 out of 100 children of the same age and sex. This growth percentile calculator works out weight-for-age and length- or height-for-age percentiles from birth to 20 years, using the WHO growth charts for babies and toddlers and the CDC growth charts for older children.

From age 2, it also calculates BMI-for-age, which the CDC uses to screen weight status: Underweight (below the 5th percentile), Healthy Weight (5th to below the 85th), Overweight (85th to below the 95th) and Obesity (95th and above). For a projection of adult height, see the Child Height Predictor.

How to Use This Growth Chart Calculator

Choose boy or girl, enter the age (in months for babies), the weight in pounds and the length or height in inches. The calculator chooses the growth chart for the age automatically and shows each percentile and z-score, and a chart comparing your child's weight with the median and screening lines for their age. If you switch charts manually, it tells you which one the CDC recommends for that age.

For babies under 2, measure length lying down; from age 2, measure standing height without shoes. Standing height is usually slightly less than lying length, which is one reason the charts change at age 2.

WHO vs. CDC growth charts: which one applies

The CDC and the American Academy of Pediatrics recommend the WHO growth charts from birth to 2 years and the CDC growth charts from 2 to 20 years. The two charts were built differently:

WHO Child Growth Standards (2006): based on healthy, breastfed children in six countries raised in good conditions. They describe how babies should grow, which is why the CDC recommends them for all infants, however they are fed.
CDC growth charts (2000): based on U.S. children measured in national surveys. They describe how U.S. children did grow, and they continue to age 20 with BMI-for-age.

The screening cut-offs also differ. On WHO charts, the CDC suggests looking more closely at measurements below the 2nd or above the 98th percentile (strictly the 2.3rd and 97.7th, two standard deviations from the median). On CDC charts, the 5th and 95th percentiles are used. A breastfed baby can look small on the CDC infant chart and normal on the WHO chart, so using the right chart matters most in the first two years.

Growth Percentile Examples

Infant: a 6-month-old baby girl

A 6-month-old girl weighs 16 lbs and is 25.5 inches long. Enter her age as 6 months and the calculator uses the WHO chart. Her weight is at the 48th percentile and her length at the 33rd percentile, both well inside the WHO screening lines of 12.6 lbs (2nd percentile) to 20.6 lbs (98th) for her age. For infant growth, the trend across checkups matters more than any single reading.

Boy: a 10-year-old boy

A 10-year-old boy weighs 75 lbs and is 54 inches tall. As a growth calculator for boys over 2, it uses the CDC boys' chart: weight at the 63rd percentile, height at the 41st percentile, and a BMI of 18.1 at the 73rd BMI-for-age percentile, in the Healthy Weight category.

Girl: a 7-year-old girl

A 7-year-old girl weighs 50 lbs and is 48 inches tall. The growth calculator for girls uses the CDC girls' chart: weight at the 49th percentile, height at the 53rd percentile, and a BMI of 15.3 at the 45th BMI-for-age percentile, right in the middle of the healthy range.

Formula Explained

Both the WHO and CDC publish three values for each sex and month of age: L (skewness), M (median) and S (coefficient of variation). The calculator interpolates L, M and S between the nearest months, converts the measurement to a z-score with the LMS formula, and converts the z-score to a percentile. This is the same method WHO and CDC use to draw their growth chart curves.

z = ((X / M)^L − 1) / (L × S) (or z = ln(X / M) / S when L = 0)
Percentile = Φ(z) × 100, where Φ is the standard normal CDF
X = weight in kg (lbs × 0.4536), length or height in cm (inches × 2.54), or BMI
BMI = (Weight in lbs / (Height in inches)²) × 703
Healthy Weight Range = BMI at the 5th and 85th percentile × (Height in inches)² / 703

Tips for Best Results

Use accurate measurements: Weigh babies without clothes or diapers, and measure length lying flat with the legs straight. For older children, use a calibrated scale and measure height standing against a wall.
Enter age in months for babies: A month makes a big difference to infant growth, so 7 months is more accurate than 0.5 years.
Track over time: One percentile is a snapshot. A steady curve across several checkups is the best sign of healthy growth.
Compare weight and length together: A baby whose weight percentile is far below their length percentile, or far above it, is worth discussing with your pediatrician.
Consult healthcare providers: Percentiles are screening tools. Talk to your child's doctor about any concern, especially a fall across two or more percentile lines.

Frequently Asked Questions

What does the 50th percentile mean?

The 50th percentile is the median: half of children of the same sex and age in the reference group measure less, and half measure more. A child at the 25th percentile for weight is heavier than 25 out of 100 children of the same age and sex. Any percentile can be healthy; what matters most is that a child follows a steady curve over time.

Should I use the WHO or CDC growth chart for my child?

The CDC and the American Academy of Pediatrics recommend the WHO growth charts from birth to 2 years, for all babies regardless of how they are fed, and the CDC growth charts from 2 years to 20 years. This calculator chooses the right chart automatically from the age you enter, and you can switch charts to compare.

Is it bad if my baby is in a low percentile?

Not necessarily. Many healthy babies sit at the 10th or 15th percentile because their parents are small. On WHO charts, the CDC suggests doctors look more closely below the 2nd percentile (about 2.3rd) or above the 98th (about 97.7th). A single low reading is a reason to talk to your pediatrician, not a diagnosis.

Is it normal for my baby to change percentiles?

Small shifts are normal, especially in the first months and around the switch from WHO to CDC charts at age 2. Pediatricians pay attention when a child crosses two or more major percentile lines (for example from the 75th to below the 25th) or when weight and length percentiles move far apart. Bring a few measurements over time to your child's checkups.

Why are there separate growth charts for boys and girls?

Boys and girls grow at different rates. Boys are slightly heavier and longer on average from birth, and in adolescence girls usually have their growth spurt earlier. Using a growth calculator for boys or girls with the matching chart makes the percentile a fair comparison.