Full-term newborns usually weigh 2.5–4.3 kg (5 lb 8 oz–9 lb 7 oz), with an average near 3.3 kg (7 lb 4 oz).
Typically, most full-term babies land between 2,500 and 4,300 grams. Most sit close to 3,300 grams. Boys tend to be a touch heavier than girls. Parents’ size, gestational age, and health during pregnancy all influence the number on the scale.
Normal Newborn Weight: How Much Do Most Babies Weigh?
Across term births, a range makes sense. A baby at 37 weeks often weighs less than one born at 40 or 41 weeks. Sex matters, with boys edging girls by roughly 100–150 grams on average. Geography and altitude can nudge figures too. That’s why a band, not a single target, describes “normal.”
On the low end, the WHO low birth weight cutoff sits below 2,500 grams. On the high end, clinicians use the term macrosomia once weight reaches four kilograms, with added caution beyond 4,500 grams; see the ACOG practice bulletin on macrosomia for standard thresholds.
Newborn Weight Categories And Thresholds
| Category | Grams (kg) | Pounds/ounces |
|---|---|---|
| Extremely Low Birth Weight | <1,000 g (1.0 kg) | <2 lb 3 oz |
| Very Low Birth Weight | 1,000–1,499 g (1.0–1.5 kg) | 2 lb 3 oz–3 lb 5 oz |
| Low Birth Weight | <2,500 g (2.5 kg) | <5 lb 8 oz |
| Typical Full-Term | 2,500–4,300 g (2.5–4.3 kg) | 5 lb 8 oz–9 lb 7 oz |
| Large For Gestational Age | ≥90th percentile for week | Varies by week |
| Macrosomia (clinical) | ≥4,000–4,499 g | ≥8 lb 13 oz–9 lb 14 oz |
| Macrosomia (higher risk) | ≥4,500 g | ≥9 lb 15 oz |
Why Weight Varies From Baby To Baby
Gestational Age
More time in the womb usually equals a heavier newborn. A term window runs from 37 through 41 completed weeks inclusive. Earlier arrivals often weigh less and may need extra feeding support.
Parents’ Size And Genetics
Smaller parents often have smaller babies. Larger parents often have larger babies. Siblings tend to cluster, though each child writes a new story.
Placenta And Cord
A well-working placenta and steady cord flow support growth. Issues with function can hold weight down. Care teams track growth patterns when placental concerns arise.
Carrying More Than One
Twins and higher-order multiples weigh less on average, since space and shared resources limit growth. They can still thrive with good feeding plans and close follow-up.
Maternal Conditions
Diabetes in pregnancy can push weight up. High blood pressure, some infections, and smoking can pull weight down. Treating health needs during pregnancy helps babies get the calories they need.
Nutrition And Weight Gain
Steady weight gain in pregnancy supports a healthy birth weight. Too little gain or poor diet can reduce fetal growth. Prenatal care teams guide targets that fit the person and the pregnancy.
Birth Weight Vs. First-Week Changes
The number you see on day one isn’t a stick-forever badge. Newborns pass meconium and shift fluids. A drop of 5–7% by day three is common. Up to 10% can occur and still be fine with close feeding support. Most regain by the end of week two. If diapers are scarce or the drop is steep, see your baby’s clinician promptly.
How And When Birth Weight Is Measured
Hospitals weigh babies soon after delivery, naked and before the first bath. Early measurement avoids the natural fluid shifts that follow. Scales read in grams. Staff record the number in the chart and on the discharge paperwork. At home, weigh-ins happen at checkups. Using the same scale and similar timing from visit to visit helps spot trends.
How Doctors Use Percentiles
The raw number matters, yet context matters too. Growth charts plot weight against age and sex. A baby near the 50th percentile matches the median for peers. Below the 10th percentile at term may suggest small for gestational age. Above the 90th may suggest large for gestational age. One point doesn’t tell the whole tale; steady gain and good feeding round out the picture.
Low Birth Weight And What It Means
“Low birth weight” equals less than 2,500 grams. This label doesn’t always mean illness. Many late preterm babies fall under the cutoff and do well. Yet the tag flags a need for closer checks on feeding, temperature, and sugar levels. Hospitals often keep these babies a little longer to be sure feeds are steady and weight is heading up.
High Birth Weight And Macrosomia
When the number hits 4,000 grams or more, teams may mention “macrosomia.” Risks climb further above 4,500 grams. Bigger size can raise the chance of shoulder dystocia with vaginal birth and may lead to a cesarean plan. After delivery, staff watch sugar levels and feeding. Plenty of big babies leave the hospital strong and healthy; the label mainly guides extra vigilance.
What Weight Loss After Birth Looks Like Day By Day
Day 1–3: Small drop as urine, stool, and fluid shift. Frequent feeds get milk supply going.
Day 4–7: Weight starts to level out. Many babies begin to gain again as milk flow increases.
Day 8–14: Birth weight is often back by the end of this window. Some hit the mark sooner.
Day 15 and beyond: Expect modest gains, tracked at each visit.
When To Seek Care
Call your baby’s clinician if you see few wet diapers, weak sucking, marked sleepiness, or jaundice. Ask for feeding help early. Weight is one sign; how the baby looks and acts matters just as much.
How Feeding Method Affects Early Weight
Breastfed babies often lose a little more in the first few days while supply builds. Bottle-fed babies may lose less at first. By two weeks, the gap usually closes. Over months, both paths support healthy growth with good technique and responsive feeding.
Practical Ways To Support Healthy Gain
Feeding Rhythm
Feed on cue, not by the clock alone. Keep the baby close and watch for early hunger cues. Skin-to-skin time steadies temperature and supports feeding readiness.
Technique Tips
Make sure the latch is deep and comfortable. Burp gently and switch sides as needed. For bottle feeds, pace the flow and pause for breathing.
Home Weighing: When It Helps
Most families don’t need a home scale. Short-term checks can help when a midwife or doctor requests closer tracking. If you weigh at home, use the same device, at the same time of day, with a dry diaper or no diaper. Log numbers rather than chasing each ounce; trends tell the story.
Preterm And Late Preterm Notes
Babies born before 37 weeks often weigh less and may need extra help with feeding and temperature. Late preterm babies (34–36 weeks) can look “term” yet tire faster at the breast or bottle. Extra support and a slower pace bring steady gains.
Weight And Length Together
Longer babies often weigh more, though not always. Length and head size matter when a doctor reviews growth. A smaller weight with a normal length can hint at calorie needs. A lower length and weight together can point to earlier timing or placental limits.
Average Term Weight By Gestational Week
| Week | Median kg | Median lb-oz |
|---|---|---|
| 37 | 3.0 | 6 lb 10 oz |
| 38 | 3.2 | 7 lb 1 oz |
| 39 | 3.3 | 7 lb 4 oz |
| 40 | 3.4 | 7 lb 8 oz |
| 41 | 3.5 | 7 lb 12 oz |
Common Myths, Clear Facts
“My baby was nine pounds, so I’ll have nine-pounders every time.” Not always. Each pregnancy is new.
“A chubby newborn means fewer night feeds.” Newborn stomachs are tiny. Frequent feeds are normal no matter the scale.
“Big babies always need a cesarean.” Many deliver vaginally with a safe, tailored plan.
“Small babies can’t breastfeed well.” With good latch help and patience, many do great.
Quick Conversions You’ll Use
2,500 g = 5 lb 8 oz; 3,000 g = 6 lb 10 oz; 3,300 g = 7 lb 4 oz; 3,400 g = 7 lb 8 oz; 3,500 g = 7 lb 12 oz; 4,000 g = 8 lb 13 oz; 4,500 g = 9 lb 15 oz.
Before You Leave The Hospital
Teams check weight trends, feeding, urine output, and jaundice risk before discharge. A plan for a follow-up weigh-in, within two to three days, helps catch feeding hurdles. Take notes.
Smart Questions For The First Visit
Ask which percentile your baby sits on today and how that compares with the birth number. Ask how many wet and dirty diapers to expect by day and by week. Leave with a clear time for the next weight check.
Why Scales Sometimes Disagree
Different devices can vary by a few ounces. Clothing, blankets, and a full diaper add weight. To get a clean read, weigh naked or with a dry diaper, at a similar time, and on the same scale when possible. If two clinic scales disagree, the team follows one device across visits for consistency.
What Counts As A Red Flag
Weight loss beyond 10% from birth, poor urine output after day four, or ongoing vomiting needs a same-day call. Trust your sense. If something seems off, seek care.
Your Takeaway
There isn’t one perfect number. A healthy range spans 2.5 to 4.3 kilograms for term babies, with many landing near 3.3. The goal is steady gain, good feeds, and a responsive newborn.