Baby Growth at Month 4: Milestones & Percentiles (2026)
Your baby is 4 months and each month brings visible changes. At this age, growth is still rapid with weekly weight gain of 100-150g and monthly length gain of about 2.5 cm. The median weight is about ${7.0 kg} (${15.4 lb}) for boys and ${6.4 kg} (${14.1 lb}) for girls. The healthy range is wide — all values are reference averages for education only, not medical advice.
Avg weight (boy)
15.4 lb · 7.0 kg
Avg weight (girl)
14.1 lb · 6.4 kg
Avg length (boy)
25.2 in · 63.9 cm
Avg length (girl)
24.4 in · 62.1 cm
Avg head circ. (boy)
16.6 in · 42.1 cm
Avg head circ. (girl)
16.1 in · 41.0 cm
Weight percentiles at 4 months
| Percentile | Boys | Girls |
|---|---|---|
| 3th | 12.3 lb · 5.6 kg | 11.0 lb · 5.0 kg |
| 15th | 13.7 lb · 6.2 kg | 12.3 lb · 5.6 kg |
| 50th (median) | 15.4 lb · 7.0 kg | 14.1 lb · 6.4 kg |
| 85th | 17.2 lb · 7.8 kg | 16.1 lb · 7.3 kg |
| 97th | 19.2 lb · 8.7 kg | 18.1 lb · 8.2 kg |
Length percentiles at 4 months
| Percentile | Boys | Girls |
|---|---|---|
| 3th | 23.5 in · 59.7 cm | 22.8 in · 57.8 cm |
| 15th | 24.3 in · 61.8 cm | 23.6 in · 59.9 cm |
| 50th (median) | 25.2 in · 63.9 cm | 24.4 in · 62.1 cm |
| 85th | 26.0 in · 66.0 cm | 25.3 in · 64.3 cm |
| 97th | 26.8 in · 68.0 cm | 26.1 in · 66.4 cm |
Head circumference percentiles at 4 months
| Percentile | Boys | Girls |
|---|---|---|
| 3th | 15.6 in · 39.6 cm | 15.2 in · 38.5 cm |
| 15th | 16.1 in · 40.8 cm | 15.7 in · 39.8 cm |
| 50th (median) | 16.6 in · 42.1 cm | 16.1 in · 41.0 cm |
| 85th | 17.1 in · 43.4 cm | 16.7 in · 42.3 cm |
| 97th | 17.6 in · 44.7 cm | 17.1 in · 43.5 cm |
Growth at 4 months: what the numbers mean
Growth at 4 months is rapid. On WHO reference charts, a baby at the 50th percentile weighs about 7.0 kg (15.4 lb) for boys and 6.4 kg (14.1 lb) for girls. Median length: 63.9 cm (25.2 in) for boys, 62.1 cm (24.4 in) for girls. Median head circumference: 42.1 cm (16.6 in) for boys, 41.0 cm (16.1 in) for girls. The breakneck newborn growth rate is moderating — this slowdown is normal, not a problem. 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 4 months
At 4 months, most babies feed every 3-4 hours. Formula-fed babies take 4-5 oz per feeding. Breastfeeding sessions last 10-15 minutes per side. Growth spurts around 3 and 4 months may cause cluster feeding for a day or two — this is normal and boosts milk supply.
Sleep at 4 months
Total sleep: 13-15 hours. Night sleep may consolidate into 5-8 hour stretches. Wake windows: 60-90 minutes. The 4-month sleep regression — sleep cycles maturing to adult-like patterns — can cause frequent night waking for 2-6 weeks. Always place baby on back to sleep on firm surface.
Play and development at 4 months
Best play: face-to-face interaction. Soft rattles and textured toys are great. Tummy time: 20-30 total minutes daily across sessions. Place toys just out of reach to encourage reaching and rolling. Read daily — your voice builds language foundations.
Milestones at 4 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.
- 1Rolls from tummy to back — often the first major gross motor milestone.
- 2Reaches for and swipes at dangling toys with improved aim.
- 3Babbling includes consonant-like sounds: 'ba,' 'ga,' 'ma' with emotional tone.
- 4May begin teething signs: drooling, gumming everything, fussiness.
When to call your pediatrician
- No visual tracking of faces/objects by 2-3 months
- No response to loud sounds
- No social smile by 3 months
- Cannot hold head steady when upright
- Fever 100.4°F (38°C) or higher under 3 months — seek immediate care
BabyPercent is educational only and not a substitute for professional medical advice.
Frequently asked questions
What is the average weight for a 4 months baby?
At the 50th percentile on WHO charts, a 4-month-old boy weighs about 7.0 kg (15.4 lb) and a girl about 6.4 kg (14.1 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 4 months baby?
At the 50th percentile, a 4-month-old boy measures about 63.9 cm (25.2 in) and a girl about 62.1 cm (24.4 in). Babies under 24 months are measured lying down (recumbent length). Reference averages only.
What is the average head size at 4 months?
At the 50th percentile, head circumference is about 42.1 cm (16.6 in) for boys and 41.0 cm (16.1 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 4-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.
How much weight should my baby gain per week at 4 months?
Weight gain averages 100-150 grams per week at 4 months. After the first week (when newborns lose up to 7-10% of birth weight), steady gain along their own curve is the goal. A baby who tracks the 15th percentile consistently is growing perfectly.
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 4 months is considered sleeping through. Every baby's sleep timeline is different.