How big are babies at birth?
Weight, length and head circumference at birth on the WHO Child Growth Standards, for girls and boys, from the 3rd percentile to the 97th. Then what the CDC and the NHS say about birth weight, in their own words.
Newborn weight, length and head circumference on the WHO standards
Girls, at birth
| Measure | 3rd | 15th | 50th (median) | 85th | 97th |
|---|---|---|---|---|---|
| Weight | 2.4 kg (5 lb 5 oz) | 2.8 kg (6 lb 3 oz) | 3.2 kg (7 lb 1 oz) | 3.7 kg (8 lb 3 oz) | 4.2 kg (9 lb 4 oz) |
| Length | 45.6 cm (18.0 in) | 47.2 cm (18.6 in) | 49.1 cm (19.3 in) | 51.1 cm (20.1 in) | 52.7 cm (20.7 in) |
| Head circumference | 31.7 cm (12.5 in) | 32.7 cm (12.9 in) | 33.9 cm (13.3 in) | 35.1 cm (13.8 in) | 36.1 cm (14.2 in) |
Boys, at birth
| Measure | 3rd | 15th | 50th (median) | 85th | 97th |
|---|---|---|---|---|---|
| Weight | 2.5 kg (5 lb 8 oz) | 2.9 kg (6 lb 6 oz) | 3.3 kg (7 lb 4 oz) | 3.9 kg (8 lb 10 oz) | 4.3 kg (9 lb 8 oz) |
| Length | 46.3 cm (18.2 in) | 47.9 cm (18.9 in) | 49.9 cm (19.6 in) | 51.8 cm (20.4 in) | 53.4 cm (21.0 in) |
| Head circumference | 32.1 cm (12.6 in) | 33.1 cm (13.0 in) | 34.5 cm (13.6 in) | 35.8 cm (14.1 in) | 36.9 cm (14.5 in) |
From the WHO Child Growth Standards, month 0. The same rows open the full tables: weight, length and head circumference.
Average birth weight, in the sources’ words
“While the average full-term baby weighs about 7 pounds (3.17 kg) at birth, a premature newborn might weigh 5 pounds (2.26 kg) or even considerably less.” American Academy of Pediatrics
“Birthweight: Low birthweight is less than 2,500 grams, and normal and higher birthweights are 2,500 grams or more.” CDC
“Low birth weight has been defined by WHO as weight at birth of < 2500 grams (5.5 pounds).” World Health Organization
“Babies born early (before 37 weeks) or with a low birth weight (less than 2.5kg or 5.5lb) are more at risk of SIDS.” NHS
“Birth weight is the first weight of your baby, taken just after being born. A low birth weight means that the baby is less than 5 pounds, 8 ounces. A high birth weight means that the baby is more than 8 pounds, 13 ounces.” MedlinePlus (NIH)
“Data are for the U.S.
Number of babies born low birthweight (less than 2500 grams): 308,966
Percent born low birthweight: 8.52%
Percent born very low birthweight (less than 1500 grams): 1.33%” CDC
“Boys and girls have different charts because boys tend to be a little heavier and taller, and their growth pattern is slightly different.” NHS
Length and head circumference at birth
“The average baby born at term in Australia:
weighs about 3.5 kg, ranging from 2.9 kg to 4.2 kg
measures about 50 cm from head to toe, ranging from 46 cm to 56 cm
has a head circumference of about 35 cm, ranging from 33 cm to 37 cm.” Raising Children Network
“The average newborn's head circumference measures about 13 ¾ inches (35 cm), growing to about 15 inches (38 cm) by 1 month.” American Academy of Pediatrics
From the birth weight on, on one chart.
Log the birth weight, length and head circumference, then every checkup after. Bundle of Joy charts them on the WHO standards with the percentile, on your phone and your partner’s, and makes a PDF for the pediatrician. Free.
Sources
- World Health Organization: WHO Child Growth Standards
- American Academy of Pediatrics: Caring for a Premature Baby: What Parents Need to Know (October 31, 2019)
- CDC: Products - Data Briefs - Number 525 - March 2025 (March 19, 2025)
- World Health Organization: Low birth weight
- NHS: Sudden infant death syndrome (SIDS) (November 25, 2025)
- MedlinePlus (NIH): Birth Weight (February 29, 2024)
- CDC: FastStats: Birthweight and Gestation (June 10, 2026)
- NHS: Your baby's weight and height (September 20, 2023)
- Raising Children Network: 40 weeks pregnant (November 22, 2023)
- American Academy of Pediatrics: Your Baby's First Month: Growth & Physical Appearance (April 3, 2026)
Every quote on this page was checked against its source on . Not medical advice: for your baby, ask your pediatrician or health visitor.
More from the sources: Baby feeding chart · Newborn diaper chart · Newborn weight loss and gain · Newborn fever · Newborn sleep · Tummy time · Bathing a newborn · Cluster feeding · Infant Tylenol and Motrin dosage · Newborn hiccups · Baby colic
Every measurement, on one chart.
Weight, height and head circumference on the WHO charts.
