1 Month Baby Weight & Height: WHO Growth Standards & Percentiles
Reviewed by Dr Abhas Gupta, MBBS, MD, DNB (Paediatrics), PDCC (Paediatric Rheumatology) • About Dr Abhas Gupta (Bio) • Last reviewed: 16 October 2026
Compare your 1-month-old baby's weight and length against official World Health Organization (WHO) international growth charts. Calculate exact Z-scores, track monthly velocity, and plot their developmental curve channel.
What's normal at 1 month
At 1 month, rapid growth velocity is fueled entirely by breastfeeding. Expect wet diapers after almost every feed and steady lengthening of sleep stretches.
Expected monthly weight gain: 750 to 900 grams per month (approx. 25–30 grams per day)
WHO Growth Standards for 1 Month Olds
According to World Health Organization (WHO) multicentre growth standards, benchmarks for 1-month-old infants are:
- Boys Median Weight: 4.5 kg (3rd centile: 3.4 kg, 97th centile: 5.7 kg)
- Girls Median Weight: 4.2 kg (3rd centile: 3.2 kg, 97th centile: 5.4 kg)
- Boys Median Length: 54.7 cm (3rd centile: 51.1 cm, 97th centile: 58.4 cm)
- Girls Median Length: 53.7 cm (3rd centile: 50 cm, 97th centile: 57.4 cm)
Normal range at 1 months
| Centile | Boys Weight (kg) | Girls Weight (kg) | Boys Length (cm) | Girls Length (cm) |
|---|---|---|---|---|
| 3rd | 3.4 | 3.2 | 51.1 | 50 |
| 50th (Median) | 4.5 | 4.2 | 54.7 | 53.7 |
| 97th | 5.7 | 5.4 | 58.4 | 57.4 |
Vaccines due at 1 months
6 Weeks visit: Hexavalent (DTP, IPV, Hib, Hepatitis B) dose 1, PCV dose 1, Rotavirus dose 1.
Feeding stage at 1 months
Exclusive Milk Feeding (0–5 Months): Exclusive breastfeeding provides 100% of fluids and nutrition. No solids, water, honey, or gripe water before 6 completed months (180 days).
Calculate Your 1 Month Old's Percentile
Frequently Asked Questions for 1 Month Olds
Is 3.2–5.4 kg (girls) or 3.4–5.7 kg (boys) normal for a 1 month old baby?
Yes. According to official World Health Organization (WHO) Child Growth Standards, the healthy normal range (3rd to 97th percentile) for a 1-month-old boy is 3.4–5.7 kg (median: 4.5 kg), and for a 1-month-old girl is 3.2–5.4 kg (median: 4.2 kg). A baby tracking steadily along any channel within this window is developing normally.
How much weight should a 1 month old gain in a month?
According to WHO growth velocity benchmarks, a healthy 1-month-old baby typically gains about 750 to 900 grams per month (approx. 25–30 grams per day). Weight gain velocity slows naturally across the first year as mobility and activity increase.
When should I worry about my 1 month old's weight?
Consult your pediatrician if your baby's weight sits below the 3rd percentile (3.4 kg for boys, 3.2 kg for girls), crosses two major percentile lines downward over consecutive months, or shows zero weight gain across two consecutive clinical checkups.