Baby Height/Length Percentile Calculator
The Baby Height/Length Percentile Calculator shows where your baby's length or height ranks against other children of the same age and sex. Enter the age, sex, and measured length, and it estimates the percentile using WHO growth references, along with the median height for that age. The 50th percentile is average; very low or very high values are worth raising with your pediatrician.
Rates and fees change frequently. Always confirm the current figures
with the official authority before relying on this result.
- Approximate estimate using WHO medians. Clinicians use full LMS charts for precise percentiles.
Formula
z = (height − median) ÷ SD; percentile from the normal distribution (WHO reference).
- The percentile compares your baby's length/height to the distribution of heights for their age and sex.
- A z-score is computed as z = (height − median) ÷ SD, then converted to a percentile using the normal distribution.
- Medians come from WHO length/height-for-age references and are interpolated between the charted ages.
- Input definitions: • Gender: boy or girl, since growth references differ by sex. • Age: the baby's age in months (0–60). • Length / Height: measured lying down (length) under 2 years, or standing (height) after.
- This is a screening estimate using approximate standard deviations — clinicians use full LMS charts for precise percentiles.
- Tracking the trend over several visits is more meaningful than any single percentile reading.
Example Calculation
Inputs
- Gender: boy
- Age: 6 months
- Length / Height: 67.6 cm
A 6-month-old boy measuring 67.6 cm sits right at the WHO median length for his age, so the estimated percentile is about the 50th — an average length.
Frequently asked questions
What does a height percentile mean?
It tells you how your baby's length/height compares with other babies of the same age and sex. The 50th percentile is average; the 90th means taller than 90% of peers.
What percentile is normal?
Roughly the 3rd to 97th percentile is considered typical. Where your baby tracks consistently matters more than the exact figure.
What's the difference between length and height?
Length is measured lying down (used under age 2) and height is measured standing (used after age 2). Standing measurements read slightly shorter.
How do I measure my baby's length?
Lay your baby flat, gently straighten the legs, and measure from the crown of the head to the bottom of the heel.
Should I worry about a low or high percentile?
Not by itself — healthy babies span the whole range. Your pediatrician looks at growth trends and your family's heights together.
How accurate is this estimate?
It uses WHO medians with approximate standard deviations, so it's a screening estimate. Clinicians use detailed LMS charts for exact percentiles.
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