Educational tool — not medical advice. Verify with a qualified healthcare professional before making clinical decisions.
How Height-for-Age Percentiles Work
Height-for-age (or length-for-age for infants) percentiles compare your child's stature to a reference population of children the same age and sex. A child at the 50th percentile is taller than 50% of children their age — this is the median, not a "target." Any percentile between the 3rd and 97th is considered within the normal range.
This calculator uses the CDC growth charts, which are the standard reference in the United States for monitoring height and length from birth to 20 years:
- CDC Length-for-Age (birth–36 months) — measures recumbent length (lying down). This is the standard for infants and toddlers who cannot stand reliably.
- CDC Stature-for-Age (2–20 years) — measures standing height. Used once a child can stand upright, typically from age 2.
There is an important measurement difference: recumbent length is typically about 1 cm longer than standing height at the same age due to spinal compression when standing. The two CDC charts overlap between 24 and 36 months to allow clinicians to transition between measurement methods.
What Matters More Than the Number
A single percentile reading is less important than the trend over time. A child consistently tracking at the 20th percentile is growing normally — they're simply shorter than average. What pediatricians watch for is a child crossing two or more major percentile lines (growth faltering), which can indicate a nutritional issue, hormonal condition, or other concern worth investigating.
Genetics play the largest role in determining a child's adult height. Children of taller parents tend to track higher percentiles, and vice versa. Your pediatrician may calculate a "mid-parental height" to estimate your child's expected adult stature.
Height-for-Age FAQ
How do I use this height percentile calculator?
Select your child's sex, enter their age (either by birth date or directly in years and months), and type their height or length. Click "Calculate Percentile" to see the result on the appropriate CDC growth chart along with a plain-language interpretation.
What is the difference between length and height?
Length is measured with the child lying down (recumbent) and is used for infants and toddlers under 2–3 years. Height is measured standing up and is used for older children. Recumbent length is typically about 1 cm longer than standing height at the same age due to spinal compression.
What is a normal height percentile for a child?
Any percentile between the 3rd and 97th is within the normal range. A child at the 15th percentile is just as healthy as one at the 85th — what matters is that they follow their own growth curve consistently over time rather than crossing multiple percentile lines.
Why does this calculator only show CDC charts?
The WHO length-for-age data is not currently included in this calculator. The CDC charts cover the full age range from birth to 20 years and are the most commonly used reference in the United States. For infants under 24 months, your pediatrician may use WHO growth standards — ask them to compare both if you have concerns.
When should I worry about my child's height?
Talk to your pediatrician if your child's height is below the 3rd percentile, or if their height percentile has crossed two or more major percentile lines (e.g., dropping from the 50th to the 10th) over several visits. Short stature can be familial (genetic) or may warrant further evaluation in some cases.
Can this calculator predict my child's adult height?
No — this calculator shows your child's current percentile compared to their peers. Predicting adult height requires additional factors like parental heights, bone age, and pubertal status. Our Height Predictor tool (coming soon) will use the Khamis-Roche method for adult height estimation.