See where your baby's weight falls against the WHO growth standards — the weight-for-age percentile and z-score for their sex and age.
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Pick the sex, enter the age in months (0–60) and the weight in kg. The percentile, WHO median and z-score update instantly.
This tool uses the WHO Child Growth Standards, which describe healthy, breastfed children. The percentile is an estimate, not a diagnosis, and the growth trend over time matters more than a single reading. Discuss any weight below the 3rd or above the 97th percentile with your pediatrician.
Percentile ≈ P48.2 · Normal rangeInformational estimate, not medical advice. We use the WHO Child Growth Standards and the LMS method. Instant in-browser calculation, no account, no data sent. For any concern about your child's growth, consult a pediatrician.
✚ Results are for informational purposes and do not replace medical advice. For health decisions, consult a doctor.
The WHO weight-for-age percentile compares your baby's weight to a reference distribution for their sex and age in months. We compute the z-score with the LMS method, then read off the percentile:
A boy aged 12 months weighing 10.5 kg: with the WHO median M = 9.6, L ≈ 0.06 and S = 0.111, the z-score is about +0.76, which converts to roughly the 78th percentile — he weighs more than about 78% of boys his age.
A percentile shows how your baby's weight compares with other babies of the same sex and age. A 60th percentile means your baby weighs more than 60% of same-age, same-sex babies and less than the other 40%.
Any value between the 3rd and 97th percentile is considered a healthy range by the WHO. There is no single best number — a baby steadily tracking the 15th percentile is as healthy as one on the 85th.
We use the WHO weight-for-age tables, which give three numbers for each sex and age: L (skew), M (median) and S (spread). The z-score is ((weight ÷ M)^L − 1) ÷ (L × S), and that z-score is then converted to a percentile.
Not on its own. The 10th percentile is within the healthy range. What matters more is the trend: a baby who consistently follows a percentile line is usually growing well. A sudden drop across several lines is what deserves attention.
They describe how healthy, breastfed children grow under good conditions, based on a large international study. Unlike older charts, they set a single standard for how children should grow, not just how they happened to grow in one country.
Talk to your pediatrician if the weight is below the 3rd or above the 97th percentile, if your baby crosses two or more percentile lines up or down, or if feeding, energy or development also seem off. This tool is a guide, not a diagnosis.