Newborn Baby Average Weight & Length at Birth

What Is Normal for a Newborn?

Full-term newborns (37–42 weeks) typically weigh between 2.5 and 4.5 kg (5.5–10 lb). The average birth weight is about 3.5 kg (7.7 lb) for boys and 3.4 kg (7.5 lb) for girls. Birth length averages around 50 cm (19.7 in) for boys and 49.3 cm (19.4 in) for girls.

Expected Weight Loss After Birth

It's completely normal for newborns to lose 5–10% of their birth weight in the first 3–5 days. This is due to fluid loss and the transition to feeding. Most babies regain their birth weight by 10–14 days. If your baby loses more than 10% or hasn't regained birth weight by two weeks, talk to your pediatrician.

Factors That Affect Birth Weight

Birth weight is influenced by gestational age, genetics (parental size), maternal nutrition and health, birth order (later babies tend to be slightly heavier), and sex (boys average slightly heavier than girls). Premature babies will be smaller — use corrected age when tracking their growth.

When to Use Growth Charts

Pediatricians plot your baby's measurements at every well-child visit. A single measurement matters less than the trend over time. Use our weight-for-age calculator or height-for-age calculator to see exactly where your baby falls on the growth curve.