Baby Weight Percentile Calculator
Estimate your infant’s weight percentile based on WHO growth standards. A helpful guide for parents tracking early development.
Track Your Baby’s Growth
Enter your baby’s details below to instantly see an illustrative estimate of their weight percentile, along with a reference to the 50th percentile (average) for their age and sex.
Infant Growth Estimator
Get an instant percentile band estimate based on WHO data.
Understanding Baby Growth
Key concepts for confident parenting
The Growth Curve
Babies grow rapidly in the first year. Doctors plot weight, length, and head circumference on a curve to ensure the baby is following a consistent, healthy trajectory over time.
Breastfed vs. Formula
WHO charts are based on breastfed infants, who tend to gain weight more rapidly in the first 2–3 months and then lean out compared to formula-fed infants. This is completely normal.
Growth Spurts
Babies experience predictable growth spurts, often around 3 weeks, 6 weeks, 3 months, and 6 months. During these times, they may feed more frequently and seem fussier.
When to Consult a Doctor
Seek advice if your baby falls below the 3rd or above the 97th percentile, fails to gain weight for several weeks, or shows signs of dehydration or lethargy.
WHO Weight-for-Age Reference
Approximate World Health Organization (WHO) weight standards for infants from birth to 24 months.
| Age | Boys 50th %ile | Boys Normal Range (3rd–97th) | Girls 50th %ile | Girls Normal Range (3rd–97th) |
|---|---|---|---|---|
| Birth | 3.3 kg | 2.5 – 4.4 kg | 3.2 kg | 2.4 – 4.2 kg |
| 3 Months | 6.4 kg | 5.0 – 8.0 kg | 5.8 kg | 4.5 – 7.5 kg |
| 6 Months | 7.9 kg | 6.4 – 9.8 kg | 7.3 kg | 5.7 – 9.3 kg |
| 9 Months | 8.9 kg | 7.1 – 11.0 kg | 8.2 kg | 6.5 – 10.5 kg |
| 12 Months | 9.6 kg | 7.7 – 12.0 kg | 8.9 kg | 7.0 – 11.5 kg |
| 18 Months | 10.9 kg | 8.8 – 13.7 kg | 10.2 kg | 8.1 – 13.2 kg |
| 24 Months | 12.0 kg | 9.7 – 15.0 kg | 11.2 kg | 9.0 – 14.8 kg |
Infant Growth FAQ
Answers to the most frequently asked questions about baby weight, percentiles, and healthy development.
A baby weight percentile shows how your baby’s weight compares to a reference population of babies of the same age and sex. For example, if your baby is in the 50th percentile, it means they weigh more than 50% of babies their age and sex, and less than the other 50%.
Minor fluctuations are completely normal as babies grow at their own pace. However, a significant drop across two or more percentile lines (e.g., from the 50th to the 15th percentile) should be discussed with a pediatrician to rule out feeding issues or underlying health concerns.
The World Health Organization (WHO) growth charts are generally recommended for children under 2 years old, as they are based on healthy, breastfed infants from diverse global populations. The CDC charts are often used for children aged 2 and older.
You should consult a healthcare provider if your baby’s weight consistently falls below the 3rd percentile, above the 97th percentile, if there is a sudden, sustained drop or spike in their growth curve, or if they are not meeting developmental milestones.
Yes, genetics play a significant role. Babies born to taller or heavier parents may naturally track along higher percentiles, while babies of smaller parents may track along lower percentiles. The key is that the baby follows their own consistent growth curve.