WHO (0–2 years) · CDC (2–20 years)
Baby Weight Percentile Calculator
Compare your baby's weight, length and head circumference with WHO growth standards. See a baby weight percentile chart by age and sex, or check CDC BMI-for-age percentiles from age two.
Boy, 6 months, on WHO Child Growth Standards
Weight · 17 lb
40th
percentile
Length · 26.5 in
44th
percentile
Head size · 17 in
45th
percentile
Percentiles aren't a test score. A child on the 15th percentile can be just as healthy as one on the 85th. What matters most is that your child keeps following their own curve over time. Ask your pediatrician if a measurement is below the 3rd or above the 97th percentile, or if your child crosses two major percentile lines (for example, from the 50th to below the 10th).
Baby weight percentile chart
WHO weight-for-age standards · Boys · birth to 24 months
Standard percentiles: 3 · 15 · 50 · 85 · 97. ● Your child
Measurements added here stay in this page session only; they are not saved to a child profile.
WHO or CDC growth chart: which should I use?
For babies from birth to age two, CDC recommends the WHO Child Growth Standards in U.S. clinical settings. This baby weight percentile calculator uses WHO weight-for-age, length-for-age and head-circumference data. From age two, CDC growth charts are recommended; the Child option here calculates CDC BMI-for-age, not weight-for-age.
Open height, weight and BMI growth curves for older children
What does a baby weight percentile mean?
A weight-for-age percentile compares a baby's weight with the reference population of the same age and sex. The 50th percentile is the median, not a target. A single point cannot show growth over time; repeated, accurately measured weights let your pediatrician assess the child's pattern.
Reading your baby's growth curve
The reference lines show WHO weight-for-age percentiles, while your child's measurements appear in terracotta. A line connecting measurements shows the recorded pattern, not a prediction. Weight alone does not assess nutrition or diagnose a problem; clinicians also consider length, feeding, health and development.
For premature babies, ask your pediatrician which chart and corrected age to use. Review unexpected changes or feeding concerns with them rather than changing feeds to reach a particular percentile.
Baby percentile charts and motor milestones: what to watch by age
Growth chart sources
What if my baby’s weight percentile drops?
A change from the 64th to the 58th percentile does not, by itself, diagnose poor growth. Different scales, clothing, age rounding and normal variation can change a result. Compare measurements taken consistently, then look at the pattern alongside feeding, length and development.
Discuss a sustained downward trend, weight loss or feeding concerns with your pediatrician. Poor feeding, fewer wet diapers or unusual sleepiness need prompt medical advice rather than repeated online calculations. Do not change formula concentration or try to reach the 50th percentile without clinical guidance.
Measurements that make the comparison more useful
- Record the measurement date, exact age, units and whether length was measured lying down or height standing up.
- Use the same reliable scale when possible. Avoid comparing a clothed home weight with an unclothed clinic weight.
- Have length and head circumference checked at a visit; small measuring errors can noticeably change their percentiles.
Corrected age for a premature baby
Corrected age subtracts the weeks a baby arrived before 40 weeks of pregnancy from their age since birth. For example, a 16-week-old baby born at 32 weeks has a corrected age of 8 weeks. AAP guidance uses corrected age when following premature babies’ development during the first two years.
This estimate does not change the chart above or saved measurements. Ask your pediatrician which age and chart to use before entering a corrected age. Babies still before their due date may need a specialist preterm chart rather than a WHO chart.
Growth chart questions parents ask
Is the 10th percentile too low?
Not necessarily. It means about 10% of the reference population of the same age and sex has a lower measurement. Your pediatrician considers the growth pattern and overall health; a percentile alone cannot determine whether a baby is underfed.
Is this a CDC baby weight percentile chart?
For babies under two, the weight comparison uses WHO standards, as CDC recommends in the United States. The growth generator switches weight and height to CDC references at age two; the percentile calculator’s Child mode reports CDC BMI-for-age, not weight-for-age.
Can I compare a breastfed baby with these standards?
Yes. WHO standards use the breastfed infant as the normative model. A breastfed baby’s pattern may differ from older CDC infant references, especially after the early months.
Why is my result different from the doctor’s chart?
Check the measurement, units, age, sex and reference standard. Rounded ages, corrected age for prematurity and different measurements can produce different results. Ask which standard the clinic uses rather than treating either number as a diagnosis.
Related baby growth and development tools
Sources and limitations
Reference curves are sampled and interpolated from WHO/CDC LMS data. These educational tools do not replace clinical assessment or a specialist chart for prematurity.
- CDC: Using WHO Growth Standard Charts
- WHO: Child Growth Standards
- CDC: Growth charts and reference data
- AAP: Corrected Age for Preemies
Guide updated November 8, 2026.
This tool is for general information and education only. It does not replace advice from your child's pediatrician, who knows your child's full history.