Average Baby Weight & Height by Age
These are the average (50th-percentile median) weight and height values from the official WHO Child Growth Standards, for boys and girls from birth to 5 years. Remember: "average" is just the middle of a wide healthy range — your baby being above or below these numbers is usually completely normal.
| Age | Boy — weight | Girl — weight | Boy — height | Girl — height |
|---|---|---|---|---|
| Birth | 3.3 kg (7.4 lb) | 3.2 kg (7.1 lb) | 49.9 cm (19.6 in) | 49.1 cm (19.3 in) |
| 1 month | 4.5 kg (9.9 lb) | 4.2 kg (9.2 lb) | 54.7 cm (21.5 in) | 53.7 cm (21.1 in) |
| 2 months | 5.6 kg (12.3 lb) | 5.1 kg (11.3 lb) | 58.4 cm (23.0 in) | 57.1 cm (22.5 in) |
| 3 months | 6.4 kg (14.1 lb) | 5.8 kg (12.9 lb) | 61.4 cm (24.2 in) | 59.8 cm (23.5 in) |
| 4 months | 7.0 kg (15.4 lb) | 6.4 kg (14.2 lb) | 63.9 cm (25.2 in) | 62.1 cm (24.4 in) |
| 5 months | 7.5 kg (16.6 lb) | 6.9 kg (15.2 lb) | 65.9 cm (25.9 in) | 64.0 cm (25.2 in) |
| 6 months | 7.9 kg (17.5 lb) | 7.3 kg (16.1 lb) | 67.6 cm (26.6 in) | 65.7 cm (25.9 in) |
| 9 months | 8.9 kg (19.6 lb) | 8.2 kg (18.1 lb) | 72.0 cm (28.3 in) | 70.1 cm (27.6 in) |
| 12 months | 9.6 kg (21.3 lb) | 8.9 kg (19.7 lb) | 75.7 cm (29.8 in) | 74.0 cm (29.1 in) |
| 15 months | 10.3 kg (22.7 lb) | 9.6 kg (21.2 lb) | 79.1 cm (31.2 in) | 77.5 cm (30.5 in) |
| 18 months | 10.9 kg (24.1 lb) | 10.2 kg (22.6 lb) | 82.3 cm (32.4 in) | 80.7 cm (31.8 in) |
| 2 years | 12.2 kg (26.8 lb) | 11.5 kg (25.3 lb) | 87.1 cm (34.3 in) | 85.7 cm (33.7 in) |
| 3 years | 14.3 kg (31.6 lb) | 13.9 kg (30.5 lb) | 96.1 cm (37.8 in) | 95.1 cm (37.4 in) |
| 4 years | 16.3 kg (36.0 lb) | 16.1 kg (35.4 lb) | 103.3 cm (40.7 in) | 102.7 cm (40.4 in) |
| 5 years | 18.3 kg (40.4 lb) | 18.2 kg (40.2 lb) | 110.0 cm (43.3 in) | 109.4 cm (43.1 in) |
Values are WHO 50th-percentile medians, rounded to one decimal. Imperial conversions are approximate. Under 2 years, the height column is recumbent length; from 2 years it is standing height.
How to use these numbers
Think of the median as the center line, not a finish line. About half of all healthy babies weigh less than these figures and half weigh more. A baby who is consistently lighter or heavier than average — but growing steadily — is usually thriving. For a precise reading, calculate your baby's exact percentile rather than comparing to the average alone.
Why length becomes height at age 2
Before age 2, babies are measured lying down (recumbent length). From age 2, they're measured standing (height), which reads about 0.7 cm shorter. The WHO standards — and our calculator — switch automatically at the 24-month mark, which is why you'll see that handled for you.
See your baby's exact percentile
Averages are a starting point. Enter your child's details for their precise WHO percentile and growth curve.
Open the Growth Calculator →Related: Baby growth percentiles explained