Weight Percentile Calculator (CDC & WHO)
Enter your child's sex, age, and weight. This calculator automatically uses the WHO standard under 2 years and the CDC standard from 2 to 20 years, and shows the P3-P97 row for that exact age.
Weight percentile (CDC standard)
54th percentile
CDC 2000 (2-20y) · z-score +0.11
| Age | P3 | P10 | P25 | P50 | P75 | P90 | P97 |
|---|---|---|---|---|---|---|---|
| 6y 0m (CDC) | 16.4 kg | 17.6 kg | 18.9 kg | 20.7 kg | 22.8 kg | 25.2 kg | 28.1 kg |
In lb: median 45.6 lb
Worked example
A 3-year-old girl at 14kg: the CDC table gives L=-1.017, M=13.87kg, S=0.1189 for 36 months. Working the LMS formula through gives z = 0.08, the 53th percentile -- close to the median, since 14kg is close to the table's M of 13.9kg.
Frequently Asked Questions
Is a low or high weight percentile a problem by itself?
Not by itself. Weight percentile only becomes a concern in context: alongside height (that's what BMI-for-age is for), alongside the trend over time (a sudden jump or drop across percentile lines matters more than the single number), and alongside how the child actually looks and feels. A single reading is a data point, not a diagnosis.
Why does the source switch from WHO to CDC at 24 months?
The WHO standards describe how healthy, breastfed infants are expected to grow, which is the recommended reference under 2 years. Past 2 years, growth patterns and the two standards' reference populations diverge enough that the CDC's own US-survey-based charts are the standard pediatric references use from that point on.
My baby's weight percentile dropped between visits -- should I worry?
A small shift, especially in the first year, is common and often not meaningful on its own. What pediatricians actually watch for is crossing two or more major percentile lines downward, or a percentile that stays flat while length/height keeps climbing. If you're seeing either, that's a conversation for your pediatrician, not this calculator.
Should I use weight-for-age or weight-for-length for my baby?
Under 2 years, weight-for-length (on the baby percentile calculator) is often more clinically useful than weight-for-age alone, because it accounts for how tall the baby already is rather than just their age. This calculator's WHO branch (under 24 months) is weight-for-age; use the baby percentile calculator for weight-for-length.
These calculators estimate from published population reference data (the CDC and WHO growth charts) and published rules of thumb -- not a diagnosis, and not a substitute for your pediatrician, who tracks your child's own growth curve over time and knows their history.