Baby Growth at Month 8: Milestones & Percentiles (2026)
Your baby is 8 months and each month brings visible changes. At this age, growth continues steadily — weight gain about 70-100g per week, length gain about 1.25 cm per month. The median weight is about ${8.6 kg} (${19.0 lb}) for boys and ${8.0 kg} (${17.6 lb}) for girls. The healthy range is wide — all values are reference averages for education only, not medical advice.
Avg weight (boy)
19.0 lb · 8.6 kg
Avg weight (girl)
17.6 lb · 8.0 kg
Avg length (boy)
27.8 in · 70.6 cm
Avg length (girl)
27.0 in · 68.7 cm
Avg head circ. (boy)
17.7 in · 45.0 cm
Avg head circ. (girl)
17.3 in · 43.9 cm
Weight percentiles at 8 months
| Percentile | Boys | Girls |
|---|---|---|
| 3th | 15.2 lb · 6.9 kg | 13.9 lb · 6.3 kg |
| 15th | 17.0 lb · 7.7 kg | 15.4 lb · 7.0 kg |
| 50th (median) | 19.0 lb · 8.6 kg | 17.6 lb · 8.0 kg |
| 85th | 21.2 lb · 9.6 kg | 19.8 lb · 9.0 kg |
| 97th | 23.6 lb · 10.7 kg | 22.5 lb · 10.2 kg |
Length percentiles at 8 months
| Percentile | Boys | Girls |
|---|---|---|
| 3th | 26.1 in · 66.2 cm | 25.2 in · 64.0 cm |
| 15th | 26.9 in · 68.4 cm | 26.1 in · 66.4 cm |
| 50th (median) | 27.8 in · 70.6 cm | 27.0 in · 68.7 cm |
| 85th | 28.7 in · 72.8 cm | 28.0 in · 71.1 cm |
| 97th | 29.5 in · 75.0 cm | 28.9 in · 73.5 cm |
Head circumference percentiles at 8 months
| Percentile | Boys | Girls |
|---|---|---|
| 3th | 16.7 in · 42.5 cm | 16.3 in · 41.4 cm |
| 15th | 17.2 in · 43.8 cm | 16.8 in · 42.7 cm |
| 50th (median) | 17.7 in · 45.0 cm | 17.3 in · 43.9 cm |
| 85th | 18.2 in · 46.3 cm | 17.8 in · 45.2 cm |
| 97th | 18.7 in · 47.6 cm | 18.3 in · 46.4 cm |
Growth at 8 months: what the numbers mean
Growth at 8 months is steady. On WHO reference charts, a baby at the 50th percentile weighs about 8.6 kg (19.0 lb) for boys and 8.0 kg (17.6 lb) for girls. Median length: 70.6 cm (27.8 in) for boys, 68.7 cm (27.0 in) for girls. Median head circumference: 45.0 cm (17.7 in) for boys, 43.9 cm (17.3 in) for girls. Growth continues at a more moderate pace — babies add fewer grams weekly but grow noticeably longer and more mobile. The single most important principle: pediatricians watch the trend across multiple visits, not any single number. A baby tracking the 15th percentile steadily is thriving as much as one at the 85th. A sudden crossing of several percentile lines gets attention — and often turns out to be measurement error, a growth spurt, or a temporary feeding bump. These values are educational references, not medical advice.
Feeding at 8 months
At 8 months, feeding becomes more efficient. Formula-fed babies take 5-7 oz per feeding, 4-5 feedings daily. Solid foods are in early exploration — breast milk or formula remains the primary nutrition source through the first year.
Sleep at 8 months
Total sleep: 12-15 hours; night sleep 9-11 hours. Night waking for feeding still normal. Separation anxiety may peak around 8-9 months. Consistent bedtime routine — bath, book, bed — helps.
Play and development at 8 months
Play is all about exploration. Cause and effect — banging, dropping, mouthing are how they learn. Sitting independently frees both hands. Board books, songs with hand motions, imitation games are perfect.
Milestones at 8 months
Every baby develops on their own timeline. These are typical skills many babies show around this age. If your baby misses several milestones, mention it to your pediatrician.
- 1Starts crawling or scooting — classic crawl, army crawl, or bottom scoot all count.
- 2Uses raking grasp to pick up small items; bangs two objects together.
- 3Shows stranger anxiety; may cry when separated from primary caregiver.
- 4Understands object permanence — looks for toy you hide under a cloth.
When to call your pediatrician
- Not sitting independently by 9 months
- No consonant babbling ('ba','da','ga') by 9 months
- Crosses several percentile lines on growth chart between visits
- No interest in people or inconsistent response to name
- Loses previously acquired skills (stopped babbling, stopped sitting)
BabyPercent is educational only and not a substitute for professional medical advice.
Frequently asked questions
What is the average weight for a 8 months baby?
At the 50th percentile on WHO charts, a 8-month-old boy weighs about 8.6 kg (19.0 lb) and a girl about 8.0 kg (17.6 lb). The healthy range from the 3rd to 97th percentile is wide. These are reference averages for education, not medical advice.
What is the average length of a 8 months baby?
At the 50th percentile, a 8-month-old boy measures about 70.6 cm (27.8 in) and a girl about 68.7 cm (27.0 in). Babies under 24 months are measured lying down (recumbent length). Reference averages only.
What is the average head size at 8 months?
At the 50th percentile, head circumference is about 45.0 cm (17.7 in) for boys and 43.9 cm (17.3 in) for girls. Head circumference is measured at every well-baby visit because it reflects healthy brain growth. Educational reference only.
When should I worry about my 8-month-old's growth?
A single number rarely matters. Call your pediatrician if your baby crosses several percentile lines between visits, is not feeding well, has very few wet diapers, or seems unusually lethargic. Trust your gut — when in doubt, call. BabyPercent is educational only, not medical advice.
WHO vs CDC growth charts — which one should I use?
The WHO charts (used by most pediatricians worldwide) are based on healthy, breastfed babies from six countries. CDC charts are based on a US reference population. For babies 0-24 months, WHO charts are the standard recommended by the CDC and AAP. Both are available on BabyPercent for comparison.
Is my 8-month-old growing enough?
Growth has slowed compared to the newborn phase — this is normal. At 8 months, weight gain averages 50-100g per week. Your baby is getting longer and more mobile, which changes the growth pattern.
When do babies sleep through the night?
'Sleeping through the night' (a 6-8 hour stretch) may happen anytime from 3-6 months, but many babies still wake once or twice until 12 months. A 5-hour stretch at 8 months is considered sleeping through. Every baby's sleep timeline is different.