Average Weight for a 6-Month-Old (WHO Percentiles)
The average weight of a 6-month-old boy and girl, the full percentile range from P3 to P97, and where your baby lands — using the WHO Child Growth Standards.
Is your 6-month-old's weight typical?
A quick weight-only check. For length, head circumference and exact age, use the full tool below.
Weight, length and head circumference at your baby's exact age in days.
Reference ranges from the WHO Child Growth Standards — not medical advice. Every baby grows differently.
Weight, length & head circumference percentiles at 6 months
The WHO reference values for a {{age}}-month-old, from the 3rd to the 97th percentile, for boys and girls. P50 is the average; anywhere from P3 to P97 is a normal, healthy measurement. Numbers are calculated directly from the WHO Child Growth Standards.
Weight-for-age
| Sex | P3 | P15 | P50 | P85 | P97 |
|---|---|---|---|---|---|
| Boys | 6.4 kg14 lb 3 oz | 7.1 kg15 lb 10 oz | 7.9 kg17 lb 8 oz | 8.9 kg19 lb 9 oz | 9.7 kg21 lb 7 oz |
| Girls | 5.8 kg12 lb 13 oz | 6.4 kg14 lb 3 oz | 7.3 kg16 lb 2 oz | 8.3 kg18 lb 4 oz | 9.2 kg20 lb 5 oz |
Length-for-age
| Sex | P3 | P15 | P50 | P85 | P97 |
|---|---|---|---|---|---|
| Boys | 63.6 cm25.0 in | 65.4 cm25.8 in | 67.6 cm26.6 in | 69.9 cm27.5 in | 71.7 cm28.2 in |
| Girls | 61.5 cm24.2 in | 63.4 cm25.0 in | 65.8 cm25.9 in | 68.1 cm26.8 in | 70.0 cm27.6 in |
Head circumference-for-age
| Sex | P3 | P15 | P50 | P85 | P97 |
|---|---|---|---|---|---|
| Boys | 41.0 cm16.2 in | 42.1 cm16.6 in | 43.3 cm17.1 in | 44.6 cm17.6 in | 45.6 cm18.0 in |
| Girls | 39.8 cm15.7 in | 40.9 cm16.1 in | 42.2 cm16.6 in | 43.6 cm17.1 in | 44.7 cm17.6 in |
P50 (highlighted) is the median — the true "average". A baby is not "behind" at P15 or "ahead" at P85; both are well within the normal range. The trend along a baby's own curve over time matters far more than a single percentile.
The 6-Month Slowdown — and Where Solids Fit In
Six months is a turning point on the curve. The rapid first-half gain starts to ease: many babies drop from roughly 140–200 g a week toward about 85–140 g (3–5 oz) a week over the second half of the year. On the chart this shows up as the line bending gently flatter — expected, not a warning sign.
This is also the usual window for starting solids, which fuels a common myth: that food will pack on weight or make babies sleep and grow faster. In reality, at 6 months milk (breast or formula) is still the main source of calories, and first foods are mostly practice with tastes and textures. Weight keeps tracking its own curve; the spoon does not redraw it.
Because the pace naturally slows here, a 6-month-old’s percentile sometimes settles slightly as their genetic growth pattern asserts itself — a very chunky younger baby may ease toward a more moderate band. A gentle drift that stays steady afterward is normal; a sharp fall across a couple of visits is what warrants a pediatrician’s eye.
Weight gain slows in the second half-year — that is the curve behaving normally, not a feeding problem. Starting solids does not accelerate growth; milk still leads at 6 months.
Sources & Limitations
Every number on this page is computed from the World Health Organization Child Growth Standards (2006) — the international reference for how breastfed children grow under optimal conditions, used by pediatricians worldwide. These are population reference ranges, not targets to hit.
- WHO — Weight-for-age standards (0–5 years, boys and girls)
- WHO — Length/height-for-age standards
- WHO — Head circumference-for-age standards
Reference ranges, not medical advice — every baby grows differently, and a healthy baby can sit anywhere from the 3rd to the 97th percentile. A low or high percentile is not a problem by itself; a curve that suddenly flattens, drops or jumps across visits is what's worth a conversation. For anything that worries you, talk to your pediatrician.
Watch the curve, not just today's number
Doudou plots your baby's weight, length and head circumference on the WHO growth curves as you log — so you see the trend that actually matters, not a one-off weigh-in. Synced between both parents.
Keep Exploring
Baby Growth Percentile Calculator
Enter your baby's exact age, weight, length and head circumference for a precise WHO percentile.
Corrected Age Calculator (for preemies)
Born early? Plot growth against corrected age, not birth age, until about 2 years — otherwise the percentile reads low.
Average Weight for a 4-Month-Old (WHO Percentiles)
Average weight, length and head circumference, with the full percentile tables.
Average Weight for a 12-Month-Old (WHO Percentiles)
Average weight, length and head circumference, with the full percentile tables.
Frequently Asked Questions
- How much should a 6-month-old weigh?
- The WHO average is about 7.9 kg (17 lb 8 oz) for a 6-month-old boy and 7.3 kg (16 lb 2 oz) for a girl. That is the 50th percentile; a healthy 6-month-old spans roughly the 3rd to the 97th percentile. The full tables for both sexes are above.
- Why has my 6-month-old’s weight gain slowed down?
- Because it is supposed to. The fast newborn-to-6-month gain tapers in the second half of the first year, so the weekly number naturally shrinks and the growth line bends flatter. As long as your baby follows their own curve, feeds well and is active, a slower pace is healthy, not a red flag.
- Will starting solids at 6 months change my baby’s weight?
- Not much, and not in the way the myth suggests. At 6 months milk still provides most calories and solids are largely practice, so first foods rarely shift the growth curve on their own. Start solids for feeding skills and iron, not as a way to bump the percentile up.
- Is the 6-month weight different for boys and girls?
- Yes — boys average a bit heavier, around half a kilogram (roughly a pound) at the 50th percentile at this age. The WHO keeps separate charts for each sex, so always compare your baby to the correct one rather than a single mixed "average".
- My 6-month-old dropped a weight percentile — is that normal?
- A small, gradual shift can be normal as a baby settles onto their genetic growth channel, especially after a chunky start. What pediatricians look at is the pattern: a steady lower curve is usually fine, while a sharp crossing of two or more percentile bands across visits is worth discussing at your next checkup.
- What is the average length and head circumference at 6 months?
- About 67.6 cm (26.6 in) length for boys and 65.8 cm (25.9 in) for girls at the 50th percentile, with average head circumference near 43.3 cm (17.1 in) for boys and 42.2 cm (16.6 in) for girls. Full percentile tables for length and head circumference are included on this page.