Average Baby Weight by Month
Medically reviewed by Safi Ullah Khan
Medically reviewed by Safi Ullah Khan · Written by Muneeb Rana · Last updated 21 October 2026
Quick answer: Average baby weight by month, from WHO growth standards: boys weigh about 3.3 kg at birth, 6.4 kg at 3 months, 7.9 kg at 6 months and 9.6 kg at 12 months; girls about 3.2, 5.8, 7.3 and 8.9 kg. A wide range is healthy. Steady growth along your baby's own curve matters more than the average.
TL;DR
- Medians: about 7.9 kg (boys) and 7.3 kg (girls) at 6 months.
- Healthy range is wide (3rd-97th percentile).
- Steady growth matters more than the average.
Here's the average baby weight by month for the first year, taken directly from the WHO weight-for-age standards that the CDC recommends for children under 2.
Baby weight chart by month
| Age | Boys median | Boys range (P3-P97) | Girls median | Girls range (P3-P97) |
|---|---|---|---|---|
| Birth | 3.3 kg (7.3 lb) | 2.5-4.3 kg | 3.2 kg (7.1 lb) | 2.4-4.2 kg |
| 1 month | 4.5 kg (9.9 lb) | 3.4-5.7 kg | 4.2 kg (9.3 lb) | 3.2-5.4 kg |
| 2 months | 5.6 kg (12.3 lb) | 4.4-7.0 kg | 5.1 kg (11.2 lb) | 4.0-6.5 kg |
| 3 months | 6.4 kg (14.1 lb) | 5.1-7.9 kg | 5.8 kg (12.8 lb) | 4.6-7.4 kg |
| 4 months | 7.0 kg (15.4 lb) | 5.6-8.6 kg | 6.4 kg (14.1 lb) | 5.1-8.1 kg |
| 5 months | 7.5 kg (16.5 lb) | 6.1-9.2 kg | 6.9 kg (15.2 lb) | 5.5-8.7 kg |
| 6 months | 7.9 kg (17.4 lb) | 6.4-9.7 kg | 7.3 kg (16.1 lb) | 5.8-9.2 kg |
| 7 months | 8.3 kg (18.3 lb) | 6.7-10.2 kg | 7.6 kg (16.8 lb) | 6.1-9.6 kg |
| 8 months | 8.6 kg (19.0 lb) | 7.0-10.5 kg | 7.9 kg (17.4 lb) | 6.3-10.0 kg |
| 9 months | 8.9 kg (19.6 lb) | 7.2-10.9 kg | 8.2 kg (18.1 lb) | 6.6-10.4 kg |
| 10 months | 9.2 kg (20.3 lb) | 7.5-11.2 kg | 8.5 kg (18.7 lb) | 6.8-10.7 kg |
| 11 months | 9.4 kg (20.7 lb) | 7.7-11.5 kg | 8.7 kg (19.2 lb) | 7.0-11.0 kg |
| 12 months | 9.6 kg (21.2 lb) | 7.8-11.8 kg | 8.9 kg (19.6 lb) | 7.1-11.3 kg |
Source: WHO Child Growth Standards, weight-for-age. Ranges rounded to 0.1 kg.
How to use this chart
A median is the middle value, not a target. Babies anywhere in the range can be healthy. Plot your baby's measurements with the growth percentile calculator and read how to read a growth chart.
Typical weight gain
Most babies regain birth weight by about 2 weeks, then gain quickly for the first 3-4 months, and more slowly after 6 months. Many double their birth weight around 4-5 months and roughly triple it by 12 months.
When to talk to your pediatrician
If your baby isn't back to birth weight by 2 weeks, crosses two major percentile lines, or has feeding problems with slow gain, ask for a review. Premature babies should be compared by corrected age.
Tracking weight in Tot
Add each weight from checkups to Tot to see a growth chart over time, alongside feeding trends.
Related: baby development month by month · growth chart tracker · 6-month-old development · baby growth spurts
Download Tot free on the App Store or Google Play. Free with ads; optional Premium.
Sources
- WHO: Weight-for-age standards: www.who.int (accessed 21 October 2026)
- WHO: Child Growth Standards: www.who.int (accessed 21 October 2026)
- CDC: WHO Growth Charts for children under 2: www.cdc.gov (accessed 21 October 2026)
Medical disclaimer:
Tot and this website give general information only. Feeding, sleep and growth ranges vary; always follow your pediatrician's advice. If your baby is unwell, contact your doctor or emergency services.
FAQ
What is the average baby weight at 6 months?
About 7.9 kg (17.4 lb) for boys and 7.3 kg (16.1 lb) for girls (WHO medians).
What is the average weight of a 1-year-old?
About 9.6 kg (21.2 lb) for boys and 8.9 kg (19.6 lb) for girls.
Is my baby underweight?
Only your pediatrician can say, using your baby's full growth curve.
Do boys weigh more than girls?
On average slightly, which is why charts are separate.
How often should my baby be weighed?
At routine checkups, or more often if your pediatrician asks.
Related guides
Track this in Tot
Tot is a free baby tracker app for iPhone and Android that logs breastfeeding, bottle feeds, sleep, diapers, growth, vaccines and medicine, and lets parents share the log with a partner or caretaker.
