Baby Weight Percentile: How to Know if Your Baby is Growing Well

Every parent wonders at some point: is my baby gaining enough weight? Are they growing normally? WHO (World Health Organization) growth charts are the most widely used scientific tool to answer this question.

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What Are Growth Percentiles?

A percentile shows where your baby falls compared to a reference population. If your baby is at the 70th percentile for weight, they weigh more than 70% of babies the same age and sex, and less than 30%.

50th percentile (P50): exactly average weight
Between P10 and P90: normal range — the vast majority of healthy babies fall here
Between P3–P10 or P90–P97: borderline values, worth monitoring
Below P3 or above P97: extreme values requiring pediatric evaluation

💡 Important: There is no "right" or "wrong" percentile. A baby at the 5th percentile may be perfectly healthy if they have always followed that curve. What matters most is the consistency of the growth trend over time.

Birth Weight: What to Expect

The average weight of a full-term newborn (40 weeks) is approximately 3.3 kg for boys and 3.2 kg for girls. A birth weight between 2.5 kg and 4.5 kg is generally considered normal.

In the first days of life, it's normal for newborns to lose up to 7–10% of their birth weight due to fluid loss. This weight is typically regained within 10–14 days.

How Babies Grow in the First 24 Months

0–3 months: approximately 200–250 g per week (fastest growth in life)
3–6 months: approximately 100–150 g per week
6–12 months: approximately 70–90 g per week
12–24 months: approximately 50–60 g per week

When to Be Concerned About Baby Weight

Baby drops two or more percentile bands quickly
Weight stagnates for several weeks
Baby eats very little or refuses food
Other symptoms appear: frequent vomiting, diarrhea, lethargy

My baby is at the 20th percentile — should I worry?

No. The 20th percentile is perfectly normal. It just means your baby weighs more than 20% of babies their age. As long as the curve is consistent, there's nothing to worry about.

Do WHO charts apply to all babies?

WHO charts were developed from breastfed babies in optimal conditions across 6 countries, and represent the international standard. While minor differences exist between ethnicities, WHO charts remain the most widely used reference worldwide.

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This article is for informational purposes. Always consult your pediatrician for personalized medical advice.