- Average birth weight: girls 7 lb 2 oz (3.2 kg), boys 7 lb 6 oz (3.3 kg), the WHO median or 50th percentile.
- The usual range (3rd to 97th percentile) is 5 lb 6 oz to 9 lb 3 oz for girls and 5 lb 8 oz to 9 lb 9 oz for boys.
- The curve matters more than the number. A baby who keeps following roughly the same line is growing well, wherever that line is.
- Born early? Use the corrected age until 2 years.
What percentile is my newborn?
Type your baby's weight and we'll open the growth percentile calculator set to birth, with your baby's percentile, curve and a plain-words verdict. Add the real birth date there for an exact result.
Newborn girls: weight, length and head percentiles (WHO)
| 3rd | 15th | 50th (average) | 85th | 97th | |
|---|---|---|---|---|---|
| Weight | 5 lb 6 oz 2.4 kg | 6 lb 2 oz 2.8 kg | 7 lb 2 oz 3.2 kg | 8 lb 4 oz 3.7 kg | 9 lb 3 oz 4.2 kg |
| Length | 18 in 45.6 cm | 18½ in 47.2 cm | 19¼ in 49.1 cm | 20 in 51.1 cm | 20¾ in 52.7 cm |
| Head | 12½ in 31.7 cm | 12¾ in 32.7 cm | 13¼ in 33.9 cm | 13¾ in 35.1 cm | 14¼ in 36.1 cm |
Newborn boys: weight, length and head percentiles (WHO)
| 3rd | 15th | 50th (average) | 85th | 97th | |
|---|---|---|---|---|---|
| Weight | 5 lb 8 oz 2.5 kg | 6 lb 5 oz 2.9 kg | 7 lb 6 oz 3.3 kg | 8 lb 9 oz 3.9 kg | 9 lb 9 oz 4.3 kg |
| Length | 18¼ in 46.3 cm | 18¾ in 47.9 cm | 19¾ in 49.9 cm | 20½ in 51.8 cm | 21 in 53.4 cm |
| Head | 12¾ in 32.1 cm | 13 in 33.1 cm | 13½ in 34.5 cm | 14 in 35.8 cm | 14½ in 36.9 cm |
WHO Child Growth Standards 2006, at birth. Length is measured lying down until 2 years. The bold column is the median; the 15th to 85th percentiles hold the middle 70% of babies.
What's typical at birth
All newborns lose some weight in the first days, as they shed extra fluid and feeding gets going. Weight gain usually starts around day 5, and babies are back to their birth weight by about 2 weeks, and that is the first thing your pediatrician checks. Birth weight says more about the pregnancy than about how your baby will grow: a small baby of small parents often stays on a low line, while a big baby may drift down a band or two in the first months.
- Checkups: this is the age of the newborn visit at 3 to 5 days old; the next one is the 1-month checkup.
How to read the table
A percentile compares your baby with 100 healthy babies of the same age and sex. The 15th percentile for weight means your baby is heavier than 15 of them and lighter than the other 85. It is not a grade: the 50th is the middle of the crowd, not the goal. Look at weight, length and head together; a baby on the 20th for weight and the 20th for length is simply a smaller baby in proportion.
Crossing two or more of the main lines over time, especially downward, is what pediatricians like to look into. The growth calculator tracks that for you: add each checkup and it draws the curve and tells you how many bands it has moved.
Born early?
A baby born before 37 weeks isn't compared with this table until their due date: until then the NICU uses preterm charts (Fenton or INTERGROWTH-21st), and from the due date on the WHO charts apply with the corrected age, counted from the due date. The corrected age calculator works it out, and the growth calculator uses it when you add the due date.
Questions
Is 5 lb 6 oz too small for a newborn girl?
That is the 3rd percentile for girls at birth: 3 in every 100 healthy girls weigh that or less. It isn't a diagnosis on its own. Your pediatrician looks at whether your baby has followed that line over time, how they are feeding and the parents' sizes; a curve that is falling across lines matters more than a low but steady one. For boys the 3rd percentile is 5 lb 8 oz (2.5 kg).
How much weight does a newborn lose after birth?
Some loss in the first days is normal for every newborn. Babies usually start gaining around day 5 and are back at their birth weight by about 2 weeks. In a study of over 100,000 breastfed newborns, almost 5% of babies born vaginally, and more than 10% of those born by C-section, had lost 10% or more of their birth weight at 48 hours. That much is when pediatricians look closely at feeding, so call yours if the loss seems large or your baby isn't back to birth weight by 2 weeks.
How big is the difference between boys and girls at birth?
On the WHO medians a boy is about 4 oz (110 g) heavier and ¼ in (0.7 cm) longer than a girl. That is why the charts are separate: a girl on the 30th percentile and a boy on the 30th weigh different amounts.
Sources
- World Health Organization, WHO Child Growth Standards (2006): the weight-for-age, length-for-age and head-circumference-for-age tables. The numbers on this page come from the LMS tables in the WHO anthro package.
- CDC, Recommended growth charts (WHO charts from birth to 2, CDC charts from 2).
- American Academy of Pediatrics, Bright Futures periodicity schedule (checkup ages and screenings).
- Flaherman V. J. et al., Early weight loss nomograms for exclusively breastfed newborns, Pediatrics 2015 (weight loss at 48 hours by delivery mode).
- AAP HealthyChildren.org, Your baby's first month: growth (weight loss in the first days and getting back to birth weight).
Spotted a mistake or an outdated figure? Write to [email protected].