Baby Weight Chart by Age (WHO Standards) with Healthy Ranges
A healthy newborn weighs around 3.2 to 3.3 kg, doubles that by about 5 months, and triples it by the first birthday. Those are the WHO averages. But “average” isn’t the point. What matters is whether your baby sits inside the healthy range for their age, and babies come in a wide healthy range. Below is the full baby weight chart by age for boys and girls, plus a tool that checks your baby’s weight against the WHO standard in seconds.
Baby weight chart by age: boys
These are WHO weight-for-age figures in kilograms. The healthy range runs from the lower to the upper number, and the middle is the average.
| Age | Healthy range (kg) | Average (kg) |
|---|---|---|
| Birth | 2.5 to 4.4 | 3.3 |
| 1 month | 3.4 to 5.8 | 4.5 |
| 2 months | 4.3 to 7.1 | 5.6 |
| 3 months | 5.0 to 8.0 | 6.4 |
| 6 months | 6.4 to 9.8 | 7.9 |
| 9 months | 7.1 to 11.0 | 8.9 |
| 12 months | 7.7 to 12.0 | 9.6 |
| 18 months | 8.8 to 13.7 | 10.9 |
| 24 months | 9.7 to 15.3 | 12.2 |
| 3 years | 11.3 to 18.3 | 14.3 |
| 4 years | 12.7 to 21.2 | 16.3 |
| 5 years | 14.1 to 24.2 | 18.3 |
Baby weight chart by age: girls
Girls sit a little lower than boys at the same age, which is normal.
| Age | Healthy range (kg) | Average (kg) |
|---|---|---|
| Birth | 2.4 to 4.2 | 3.2 |
| 1 month | 3.2 to 5.5 | 4.2 |
| 2 months | 3.9 to 6.6 | 5.1 |
| 3 months | 4.5 to 7.5 | 5.8 |
| 6 months | 5.7 to 9.3 | 7.3 |
| 9 months | 6.5 to 10.5 | 8.2 |
| 12 months | 7.0 to 11.5 | 8.9 |
| 18 months | 8.1 to 13.2 | 10.2 |
| 24 months | 9.0 to 14.8 | 11.5 |
| 3 years | 10.8 to 18.1 | 13.9 |
| 4 years | 12.3 to 21.5 | 16.1 |
| 5 years | 13.7 to 24.9 | 18.2 |
Check your baby’s weight for their age
Pick boy or girl, enter the age, and add the weight to see if it falls in the healthy WHO range. It interpolates between the chart points, so an in-between age like 7 months works too.
How to read the baby weight chart by age
A single number tells you less than the trend. A baby at the lower edge of the range who gains steadily month after month is usually fine. A baby who was tracking well and then suddenly flattens or drops is the one to watch. Doctors care about the growth curve, not one weigh-in. So use the chart to spot the range, but look at the direction over several months.
A few normal patterns that surprise parents:
- Most babies lose a little weight in the first week, then regain it by about two weeks.
- Growth is fastest in the first few months and slows down after six months. A slower gain in the second half of the first year is expected, not a problem.
- Breastfed and formula-fed babies grow at slightly different rates. The WHO chart is based on breastfed babies, which is the healthy reference.
When to see a doctor about weight
Talk to your doctor if your baby’s weight falls below the healthy range for their age, crosses downward across the range over time, or hasn’t gained for several weeks. Also check in if your baby is above the range and gaining very fast. These aren’t emergencies by themselves, but they’re worth a professional look rather than guessing at home. Bring your baby’s growth records so the doctor can see the full curve.
Frequently asked questions
What is the normal weight for a 6-month-old baby?
A 6-month-old boy healthily weighs 6.4 to 9.8 kg, with an average of 7.9 kg. A 6-month-old girl healthily weighs 5.7 to 9.3 kg, averaging 7.3 kg. Anywhere inside that range is normal, so don’t worry if your baby isn’t exactly on the average.
How much weight should a baby gain each month?
In the first 3 months, babies gain roughly 150 to 200 grams a week, which slows over the first year. Most babies double their birth weight by about 5 months and triple it by 12 months. Steady gain matters more than hitting an exact number.
Is my baby underweight?
Your baby may be underweight if their weight sits below the healthy range for their age and sex on the WHO chart, especially if the gain has slowed or stopped. One low reading isn’t a diagnosis. The weight tool above flags when a figure is below range, but a doctor should confirm it.
Why is the WHO chart based on breastfed babies?
The WHO standard uses breastfed babies as the healthy growth reference, because breastfeeding is the recommended norm. Formula-fed babies sometimes gain a bit faster. That’s why a slightly different curve doesn’t automatically mean a problem.
Does a bigger baby mean a healthier baby?
No. Being above the healthy range is not a sign of better health and can carry its own risks. A healthy baby is one who stays within the range and grows along a steady curve, whether they sit near the lower or upper end.
