Average Baby Weight by Month (0–12 Months): WHO Reference Table

You just got home from the pediatrician and the nurse handed you a number — your baby's weight. Now you're staring at it wondering: is that good? Should it be more? The short answer is that the number alone tells you very little without context. What matters is whether your baby's weight is increasing in a consistent pattern over time.

Here's the complete WHO reference table — and more importantly, how to read it properly.

WHO Average Baby Weight by Month: Boys

The WHO Child Growth Standards are the global benchmark used by most pediatricians worldwide. They're based on data from 8,440 children raised under optimal conditions across six countries, providing the most representative picture of healthy infant growth.

Source: WHO Child Growth Standards — Weight-for-age, boys

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WHO Average Baby Weight by Month: Girls

Girls follow a slightly different growth curve — typically tracking about 300–500 g lighter than boys of the same age throughout the first year.

Source: WHO Child Growth Standards — Weight-for-age, girls

How Much Weight Do Babies Gain Each Month?

The rate of gain matters as much as the absolute weight. Here's what typical weekly gain looks like by age range:

What the Tables Don't Tell You

These tables show medians and percentile bands. They don't capture:

• Birth order differences. Second and third children are often born heavier than firstborns.
• Breastfed vs. formula-fed patterns. Breastfed babies tend to gain faster in months 1–3, then slightly slower from 3–12 months compared to formula-fed babies. Both are healthy.
• Genetic context. Two small parents will likely have a small baby — consistently in the 10th percentile doesn't mean a baby is undernourished.
• Prematurity. Premature babies should be tracked using corrected age (age from due date, not birth date) until at least 24 months.

Newborn Weight in the First Two Weeks

The first two weeks deserve special attention. The pattern follows a predictable arc:

1. Days 1–3: Newborns lose 5–7% of birth weight as they shed amniotic fluid and meconium, and milk supply establishes
2. Days 3–5: Weight loss typically reaches its lowest point
3. Days 5–14: Weight starts to return — most babies regain birth weight by day 10–14

If your baby loses more than 10% of birth weight, or hasn't regained birth weight by 2 weeks, contact your pediatrician — this may indicate a feeding issue or underlying concern. See normal newborn weight loss after birth for a detailed breakdown of what's expected in those first two weeks.

When to Call Your Doctor About Weight

The situations that warrant a call:

Call within a few days (non-urgent):

• Your baby's weight falls below the 3rd percentile from a previously higher position
• Your baby has dropped across two major percentile lines (e.g., 75th → 50th → 25th) over several visits
• Weight gain has stalled for more than 2–3 weeks after 1 month of age

For a detailed breakdown of which patterns are concerning vs. normal variation, see when to worry about baby weight.

Call same day or go to urgent care:

• Your newborn loses more than 10% of birth weight
• Your baby under 3 months has not regained birth weight by day 14
• You notice significant swelling or rapid, unexplained weight gain

Understanding Your Baby's Personal Curve

The most reassuring thing you can know is this: your baby's growth curve is unique to them. A baby who has been consistently at the 15th percentile since birth is growing exactly as expected. A baby who was at the 75th and drops to the 40th over two visits is worth a closer look — not because 40th is bad, but because the drop is unexpected.

Focus on the direction and consistency of the curve, not the number itself.