Child Growth Percentile Calculator
Find out how your child's height, weight and BMI compare with other children of the same age and sex. This free calculator uses the official CDC growth chart data for boys and girls aged 2 to 20 years.
What is a growth percentile?
A growth percentile shows how a child's measurement compares with a large reference group of children of the same age and sex. If your daughter is on the 70th percentile for height, she is taller than 70 out of 100 girls her age and shorter than 30. The 50th percentile is the middle, or average. Percentiles are not grades: a child on the 20th percentile can be just as healthy as one on the 80th.
How this calculator works
This calculator uses the CDC 2000 Growth Charts for children aged 2 to 20 years, the same charts used by paediatricians in the United States and many other countries. For each age and sex, the CDC publishes three values called L, M and S, which describe the shape of the growth curve. Your child's measurement is converted into a z-score using the formula Z = ((X ÷ M)L − 1) ÷ (L × S), where X is the height, weight or BMI. The z-score is then turned into a percentile. For BMI above the 95th percentile, the calculator uses the CDC's 2022 extended BMI-for-age method, which gives more accurate results for children with severe obesity.
Height, weight and BMI percentiles explained
Height-for-age shows how tall your child is compared with others of the same age. Height is strongly influenced by genetics, so children of tall parents often sit on higher percentiles.
Weight-for-age shows how heavy your child is compared with others of the same age. On its own it does not tell you whether a child is underweight or overweight, because it does not account for height.
BMI-for-age combines height and weight and is the main measure doctors use to check whether a child's weight is healthy for their height, age and sex.
BMI-for-age categories for children
| BMI-for-age percentile | Weight status |
|---|---|
| Below the 5th percentile | Underweight |
| 5th to below the 85th percentile | Healthy weight |
| 85th to below the 95th percentile | Overweight |
| 95th percentile or above | Obesity |
Adult BMI categories (such as 25 for overweight) do not apply to children, because body fat changes a lot as children grow and differs between boys and girls. That is why a child's BMI must always be compared with growth charts. For adults aged 20 and over, use our BMI Calculator.
What percentile is normal for a child?
For height and weight, any percentile between roughly the 3rd and 97th is generally considered within the normal range. What matters most is that your child grows steadily along a similar percentile line over time. Doctors may look more closely if a child is below the 3rd or above the 97th percentile, or if they cross two or more major percentile lines (for example, dropping from the 75th to the 25th) within a short time.
How to measure your child accurately
Height: have your child stand barefoot with heels, back and head against a flat wall, looking straight ahead. Place a flat object such as a book on top of their head, mark the wall, and measure from the floor to the mark. Weight: use a digital scale on a hard floor, with your child in light clothing and no shoes, ideally at the same time of day each time. Measuring every few months is enough to see a trend.
Why is my child's percentile low or high?
Most children who are small or large for their age are perfectly healthy and simply following their family's build. Other factors include when puberty starts, diet, activity levels, sleep and, less often, medical conditions. Children in South Asia may on average sit on slightly different percentiles than the US reference group, which is another reason why the growth trend matters more than one number. Your child's doctor can put the percentile in context with their full history.
Frequently Asked Questions
What does the 50th percentile mean?
The 50th percentile is the middle of the range. A child on the 50th percentile for height is taller than half of children of the same age and sex, and shorter than the other half.
Is a low percentile bad?
Not necessarily. A child on a low percentile who grows steadily along it is usually healthy. Doctors pay more attention to children below the 3rd percentile or those whose percentile drops sharply over time.
Why does this calculator only work from age 2?
The CDC recommends the WHO growth standards for babies and toddlers under 2, because they are based on healthy breastfed infants. The CDC charts used here cover ages 2 to 20.
What is a healthy BMI for a child?
A healthy BMI for a child is one between the 5th and 85th percentile for their age and sex. The actual BMI number that falls in this range changes with age, which is why percentiles are used.
What is a z-score?
A z-score shows how many standard deviations a measurement is from the average. A z-score of 0 equals the 50th percentile, +2 is about the 98th percentile, and −2 is about the 2nd percentile.
How often should I check my child's growth?
Every 3 to 6 months is enough for most children. Growth happens in spurts, so a single measurement can be misleading. Tracking over time gives a clearer picture.