4-Month-Old Baby Weight & Length Chart
Four months marks the mid-point of infancy's fastest growth phase. The 4-month sleep regression is real — many babies who were sleeping well suddenly wake more often.
Boy — 50th %ile
Girl — 50th %ile
⚖️ Weight by Percentile
| Percentile | 👦 Boy | 👧 Girl |
|---|---|---|
| 5th Percentile | 13 lbs 0 oz | 11 lbs 14 oz |
| 10th Percentile | 13 lbs 7 oz | 12 lbs 6 oz |
| 25th Percentile | 14 lbs 5 oz | 13 lbs 4 oz |
| 50th Percentile (median) | 15 lbs 7 oz | 14 lbs 2 oz |
| 75th Percentile | 16 lbs 9 oz | 14 lbs 16 oz |
| 90th Percentile | 17 lbs 7 oz | 15 lbs 14 oz |
| 95th Percentile | 18 lbs 1 oz | 16 lbs 9 oz |
📏 Length/Height by Percentile
| Percentile | 👦 Boy | 👧 Girl |
|---|---|---|
| 5th Percentile | 2' 0.3" | 1' 11.6" |
| 10th Percentile | 2' 0.5" | 1' 11.8" |
| 25th Percentile | 2' 0.8" | 2' 0.1" |
| 50th Percentile (median) | 2' 1.2" | 2' 0.4" |
| 75th Percentile | 2' 1.5" | 2' 0.8" |
| 90th Percentile | 2' 1.8" | 2' 1.1" |
| 95th Percentile | 2' 2" | 2' 1.3" |
📊 What Does My Baby's Percentile Mean?
A baby at the 50th percentile weighs more than 50% of babies the same age. The 25th–75th percentile range is considered average. Any percentile from the 5th to the 95th is medically normal — your baby's growth curve matters more than their rank. A consistently healthy 10th-percentile baby is thriving; a baby who drops from the 70th to the 30th percentile warrants a conversation with your pediatrician.
🌟 Developmental Milestones
- Rolls from tummy to back
- Reaches and grasps objects with both hands
- Babbles consonant sounds (ba, ma)
- Bears weight on legs when held standing
The 4-month sleep regression is caused by a shift to more adult-like sleep cycles. It typically lasts 2–6 weeks. Avoid starting solids early to help — it doesn't.
🍼 Feeding at 4 Month Old
Breastfed: 6–8 feeds per day. Formula: 5–6 oz every 3–4 hours (~24–32 oz/day). Solids are NOT recommended until 6 months.
🚨 Talk to Your Pediatrician If…
- Doesn't watch things as they move
- Doesn't smile at people
- Can't hold head steady
- Doesn't push down with legs on firm surface
Frequently Asked Questions
How much should a 4-month-old weigh?
WHO median is 7.0 kg (15.4 lbs) for boys and 6.4 kg (14.1 lbs) for girls. Healthy range: roughly 5.9–8.2 kg (13.0–18.1 lbs).
What causes the 4-month sleep regression?
Around 4 months, babies' sleep architecture permanently shifts to include more light-sleep cycles similar to adults. They now partially wake between cycles and must learn to self-settle.
Can I start solid foods at 4 months?
The AAP recommends waiting until 6 months for solid foods. Starting earlier doesn't improve sleep and may increase allergy risk.
My baby rolled off the bed. What should I do?
Most falls from low heights (under 3 feet) don't cause serious injury, but always call your pediatrician if it happens. Go to the ER if your baby loses consciousness, vomits repeatedly, or seems unusually sleepy.