1 week old baby weight
On the WHO growth standard, the average (median) 1-week-old baby boy weighs 3.5 kg (7 lb 11 oz) and the average girl weighs 3.3 kg (7 lb 6 oz). The usual range, from the 3rd to the 97th percentile, is 2.6–4.5 kg for boys and 2.5–4.4 kg for girls.
Weight percentiles at 1 week (WHO)
The median (50th percentile) is the average weight for this age.
| 3rd | 15th | Median | 85th | 97th | |
|---|---|---|---|---|---|
| Boys (kg) | 2.63 | 2.99 | 3.49 | 4.04 | 4.54 |
| Boys (lb) | 5.8 | 6.6 | 7.7 | 8.9 | 10.0 |
| Girls (kg) | 2.51 | 2.86 | 3.34 | 3.87 | 4.35 |
| Girls (lb) | 5.5 | 6.3 | 7.4 | 8.5 | 9.6 |
Gain since birth
Going by the WHO medians, a boy gains about 141 g (0 lb 5 oz) and a girl about 107 g (0 lb 4 oz) between birth and 1 week.Most babies lose some weight in the first days and are back to birth weight by about 10 to 14 days.
Check your baby’s weight percentile
Enter the exact date of birth for a precise result, or use the pound table below.
Enter a date of birth and at least one measurement to see the percentile.
What percentile is my 1 week old’s weight in pounds?
WHO percentile for each weight at exactly 1 week. A few days older or younger shifts it slightly.
| Weight | Boy | Girl |
|---|---|---|
| 5 lb 8 oz (2.49 kg) | 1st | 3rd |
| 6 lb (2.72 kg) | 5th | 9th |
| 6 lb 8 oz (2.95 kg) | 13th | 20th |
| 7 lb (3.18 kg) | 26th | 37th |
| 7 lb 8 oz (3.40 kg) | 43rd | 55th |
| 8 lb (3.63 kg) | 61st | 72nd |
| 8 lb 8 oz (3.86 kg) | 76th | 84th |
| 9 lb (4.08 kg) | 87th | 92nd |
| 9 lb 8 oz (4.31 kg) | 93rd | 96th |
| 10 lb (4.54 kg) | 97th | 99th |
Length and head size at 1 week
WHO percentiles in cm; the median is also shown in inches.
| 3rd | 15th | Median | 85th | 97th | Median (in) | |
|---|---|---|---|---|---|---|
| Length, boys | 47.5 | 49.1 | 51.1 | 53.1 | 54.7 | 20.1 |
| Length, girls | 46.8 | 48.4 | 50.3 | 52.3 | 53.9 | 19.8 |
| Head, boys | 32.9 | 33.9 | 35.2 | 36.4 | 37.5 | 13.8 |
| Head, girls | 32.4 | 33.3 | 34.6 | 35.8 | 36.7 | 13.6 |
Common questions
How much should a 1-week-old baby weigh?
On the WHO growth standard, the average (median) 1-week-old baby boy weighs 3.5 kg (7 lb 11 oz) and the average girl weighs 3.3 kg (7 lb 6 oz). The usual range, from the 3rd to the 97th percentile, is 2.6–4.5 kg for boys and 2.5–4.4 kg for girls.
What percentile is 8 lb at 1 week?
On the WHO chart, 8 lb (3.6 kg) at exactly 1 week is about the 61st percentile for a boy and the 72nd for a girl. The table on this page gives the percentile for every half pound in the usual range.
How much weight should a baby gain by 1 week?
Going by the WHO medians, a boy gains about 141 g (0 lb 5 oz) between birth and 1 week, and a girl about 107 g (0 lb 4 oz). Most babies lose some weight in the first days and are back to birth weight by about 10 to 14 days, so the first weeks can look flat.
What is the average length and head size of a 1-week-old?
At 1 week, the WHO median length is 51.1 cm (20.1 in) for boys and 50.3 cm (19.8 in) for girls, and the median head circumference is 35.2 cm (13.8 in) for boys and 34.6 cm (13.6 in) for girls.
Is my 1-week-old underweight?
A weight between the 3rd and the 97th percentile is within the usual range, and a baby who keeps following roughly the same percentile line is growing steadily. Talk to your pediatrician if the weight is below the 3rd percentile, if your baby is not back to birth weight by about two weeks, or if the curve drops across two of the main percentile lines.
Full charts: newborn weight chart by week · length by week · head size by week · weight by month · weight gain per week
Source: WHO Child Growth Standards, expanded daily tables, at day 7. For information only; not medical advice.