Average Newborn Weight by Sex — Reference Table
These WHO birth weight reference rows give a quick picture of where newborn measurements can fall at birth for boys and girls. They are useful for orientation, but gestational age, feeding history, and early follow-up weights matter just as much as the initial newborn weight chart position.
Boys Birth Weight WHO
WHO percentile reference rows at birth
WHO boys birth weight reference values shown in kilograms and pounds.| Percentile | Weight (kg) | Weight (lbs) |
|---|
| P3 | 2.5 | 5.5 lbs |
| P10 | 2.8 | 6.2 lbs |
| P50 | 3.3 | 7.3 lbs |
| P90 | 3.9 | 8.6 lbs |
| P97 | 4.4 | 9.7 lbs |
Girls Birth Weight WHO
WHO percentile reference rows at birth
WHO girls birth weight reference values shown in kilograms and pounds.| Percentile | Weight (kg) | Weight (lbs) |
|---|
| P3 | 2.4 | 5.3 lbs |
| P10 | 2.7 | 6.0 lbs |
| P50 | 3.2 | 7.1 lbs |
| P90 | 3.8 | 8.4 lbs |
| P97 | 4.2 | 9.3 lbs |
Weight Change in First 2 Weeks
Reference timing for typical newborn weight change after birth
Day 1–3Lose up to 7–10% of birth weight (normal)
Day 4–5Weight loss stops, begins to recover
Day 10–14Most babies back to birth weight
3 weeksSteady gain begins (~150–200g/week)
What Is a Normal Birth Weight Percentile?
A normal birth weight percentile usually sits somewhere between about P3 and P97 on a newborn weight chart. The WHO median is about 3.3 kg, or 7.3 lbs, for boys and 3.2 kg, or 7.1 lbs, for girls. Low birth weight is a separate medical definition below 2.5 kg, not just a percentile label. That is why normal birth weight percentile, average newborn weight, and clinical context should be interpreted together.
What Affects a Newborn's Birth Weight?
Factors affecting birth weight include gestational age, placental function, maternal nutrition during pregnancy, genetics, and the overall pregnancy course. Twins and higher-order multiples are also more likely to be smaller at birth than singletons. A baby birth weight percentile therefore reflects more than body size alone. It is a snapshot of how pregnancy timing, fetal growth, and inherited build came together by the time of delivery.
Weight Loss in the First Week — What Is Normal?
Newborn weight loss first week patterns can look alarming if parents expect the number to rise immediately. In reality, many babies lose up to about 10% of birth weight during the first 3 to 5 days because of fluid shifts and feeding adjustment. Normal newborn weight loss may recover a bit more slowly in breastfed babies than formula-fed babies, but most newborns are back to birth weight by roughly day 10 to day 14.
How Newborn Weight Connects to the First-Year Growth Chart
A newborn growth chart starts at birth, but that first dot does not decide every later percentile. Some babies show catch-up growth, some settle into a lower or higher family pattern, and many shift once early feeding is established. For that reason, newborn weight should be rechecked around 2 weeks, 1 month, and 2 months. Those follow-up points tell you more about baby weight gain first month patterns than birth weight alone.
If you want the longer infant tracking view after the birth visit, move from this page to the baby growth chart calculator. If the later comparison you need is around the first birthday, see average weight for a 1 year old.
When to Talk to Your Pediatrician About Birth Weight
Low birth weight percentile results near or below P3, or unusually high results above P97, are worth discussing with a clinician even when the newborn otherwise appears well. Families should also seek follow-up when a baby has not returned to birth weight by about 2 weeks, struggles to feed, seems sleepy, or has fewer wet diapers than expected. This tool helps explain when to worry about newborn weight, but it does not replace medical advice.
For the standards background behind these infant references, read the WHO vs CDC growth chart comparison. For broader parent questions about growth charts and percentiles, the growth chart FAQ collects the most common follow-up topics.