Baby Growth Chart By Age: Complete Guide to Tracking Your Child's Development
Understand baby growth charts by age with WHO and CDC standards. Learn how to read percentiles, track milestones, and know when growth patterns need medical attention.
Baby growth charts are the primary tool pediatricians use to assess whether your child is developing typically. These charts plot your baby's weight, length, and head circumference against age-based percentiles from thousands of healthy children. Understanding how to read and interpret these charts removes anxiety and helps you spot potential issues early.
What Are Baby Growth Charts
Growth charts are standardized graphs that compare your baby's measurements (weight, length, head circumference) to population data. The World Health Organization (WHO) publishes charts based on breastfed babies from six countries, representing optimal growth under ideal conditions. The CDC provides charts for U.S. children ages 2-20.
For babies 0-24 months, WHO charts are the global standard. They show percentile curves (5th, 10th, 25th, 50th, 75th, 90th, 95th) that represent where most healthy babies fall at each age.
Baby Growth Chart: Birth to 12 Months
Average Weight Milestones
| Age | Boys (50th percentile) | Girls (50th percentile) |
|---|---|---|
| Birth | 7.5 lbs (3.4 kg) | 7.2 lbs (3.3 kg) |
| 1 month | 9.8 lbs (4.4 kg) | 9.2 lbs (4.2 kg) |
| 3 months | 14.1 lbs (6.4 kg) | 12.9 lbs (5.9 kg) |
| 6 months | 17.5 lbs (7.9 kg) | 16.1 lbs (7.3 kg) |
| 9 months | 20.1 lbs (9.1 kg) | 18.5 lbs (8.4 kg) |
| 12 months | 22.5 lbs (10.2 kg) | 20.7 lbs (9.4 kg) |
Average Length Milestones
| Age | Boys (50th percentile) | Girls (50th percentile) |
|---|---|---|
| Birth | 19.7 in (50 cm) | 19.4 in (49.2 cm) |
| 3 months | 24.2 in (61.4 cm) | 23.6 in (59.8 cm) |
| 6 months | 26.6 in (67.5 cm) | 25.7 in (65.3 cm) |
| 9 months | 28.3 in (71.9 cm) | 27.6 in (70 cm) |
| 12 months | 29.9 in (75.9 cm) | 29.1 in (74 cm) |
Babies typically double their birth weight by 5 months and triple it by 12 months. Boys are generally slightly heavier and longer than girls at each milestone, though individual variation is normal.
Understanding Percentiles
The percentile number tells you what percentage of babies weigh less than your child at that age. A baby at the 50th percentile is right at the median weight, heavier than 50% of babies and lighter than the other 50%.
What percentiles mean:
- 5th percentile: 95% of babies weigh more
- 25th percentile: 75% of babies weigh more
- 50th percentile: Half weigh more, half weigh less (average)
- 75th percentile: 25% of babies weigh more
- 95th percentile: Only 5% of babies weigh more
The percentile itself matters less than consistency. A baby tracking along the 10th percentile is healthy if they stay near that curve. A baby jumping from the 75th to the 25th percentile over 2-3 months needs evaluation.
Baby Growth Chart: 12 to 36 Months
Growth velocity slows significantly after the first year. Toddlers gain approximately 3-5 pounds per year between ages 1-3, compared to 15+ pounds in the first year.
Toddler Average Weight
| Age | Boys (50th percentile) | Girls (50th percentile) |
|---|---|---|
| 15 months | 24.3 lbs (11 kg) | 22.5 lbs (10.2 kg) |
| 18 months | 25.6 lbs (11.6 kg) | 24 lbs (10.9 kg) |
| 24 months | 28 lbs (12.7 kg) | 26.5 lbs (12 kg) |
| 36 months | 31.3 lbs (14.2 kg) | 30 lbs (13.6 kg) |
Toddler Average Height
| Age | Boys (50th percentile) | Girls (50th percentile) |
|---|---|---|
| 15 months | 31.2 in (79.2 cm) | 30.4 in (77.2 cm) |
| 18 months | 32.4 in (82.3 cm) | 31.6 in (80.3 cm) |
| 24 months | 34.2 in (86.8 cm) | 33.5 in (85 cm) |
| 36 months | 37.1 in (94.2 cm) | 36.5 in (92.7 cm) |
During this period, children slim down as they become more active. It is normal for toddlers to move down 1-2 percentile curves as they shift from baby fat to leaner builds.
How to Use Baby Growth Charts
Step 1: Plot Current Measurements
Your pediatrician plots weight, length, and head circumference at each visit. You can do this at home using WHO growth chart PDFs or apps designed for tracking.
Step 2: Look for the Curve
Find where your baby's measurements fall on the percentile curves. A baby at the 60th percentile for weight is heavier than 60% of babies their age.
Step 3: Track Trends Over Time
Growth velocity (rate of change) matters more than absolute percentiles. Plot 3-4 measurements over several months. Healthy babies follow a consistent curve, staying within roughly the same percentile range.
Step 4: Compare All Three Measurements
Look at weight, length, and head circumference together. A baby at the 90th percentile for all three is proportionally large. A baby at the 90th for weight but 25th for length may have a weight issue.
How To Find Your Baby's Percentile
Quick Manual Method:
- Locate the measurement value on the growth chart's left or right side (weight in pounds/kg or length in inches/cm)
- Find your baby's age in months along the top or bottom of the chart
- Follow both lines until they intersect on the graph
- Read the percentile curve closest to where these lines cross
The percentile curve your baby lands on or near indicates their growth percentile. For example, landing between the 50th and 75th percentile curves means your baby is around the 60th-65th percentile.
The Easier Way: Apps like GrowthKit eliminate the manual plotting. Enter your baby's weight, height, and age, and the app instantly calculates exact percentiles using WHO and CDC standards. You get precise percentile numbers, growth velocity calculations, and visual trend charts without deciphering printed graphs. The app plots every measurement automatically and shows whether your baby is maintaining their growth curve over time.
When to Worry: Red Flags in Growth Patterns
Contact your pediatrician if you notice:
Concerning weight patterns:
- Crossing 2+ percentile curves downward (falling off growth curve)
- No weight gain for 2+ months under age 6 months
- Weight loss after regaining birth weight
- Weight-for-length above 95th percentile (possible overweight)
- Weight-for-length below 5th percentile (possible underweight)
Concerning length patterns:
- Consistently below 3rd percentile
- Dropping 2+ percentile curves
- Significant difference between weight and length percentiles
Concerning head circumference:
- Above 98th percentile or below 2nd percentile
- Rapid increase crossing percentile curves
- Flat growth over several months
These patterns may indicate feeding issues, metabolic conditions, hormonal problems, or other health concerns requiring evaluation.
Boys vs Girls: Why Separate Charts Matter
Boys and girls grow at different rates and have different body compositions. Boys are typically 2-3% heavier and 1-2% longer than girls at birth, and this gap widens through childhood.
Using gender-specific charts ensures accurate comparison. A girl plotted on a boys' chart will appear smaller than she actually is relative to other girls.
WHO vs CDC Charts: Which Should You Use
WHO Charts (0-24 months):
- Based on breastfed babies from optimal conditions
- Represent how babies should grow
- International standard
- Recommended by AAP for ages 0-2
CDC Charts (2-20 years):
- Based on U.S. children including formula-fed babies
- Represent how U.S. children do grow
- Used after age 2
- Include BMI-for-age after 2 years
Most pediatricians use WHO charts for babies and toddlers, switching to CDC charts at age 2. Some use CDC throughout for continuity. Ask your pediatrician which charts they prefer.
Growth Velocity: The Missing Piece
Percentiles show where your baby stands today. Growth velocity shows whether they are maintaining their growth trajectory.
Expected growth velocity:
- 0-3 months: 150-200g per week (5-7 oz)
- 4-6 months: 100-150g per week (3.5-5 oz)
- 7-12 months: 70-90g per week (2.5-3 oz)
- 1-2 years: 200-300g per month (7-10 oz)
Calculate velocity: (Current weight minus previous weight) divided by weeks between measurements equals weekly gain. A baby at the 10th percentile gaining 180g/week at 2 months is thriving. A baby at the 50th percentile gaining nothing is concerning.
Premature Babies and Adjusted Age
Premature babies use corrected age for growth charts until age 2. Subtract the weeks early from their chronological age.
Example: A baby born 8 weeks early is 6 months old chronologically but plots at 4 months (6 months minus 8 weeks) on the growth chart.
After age 2, most premature babies catch up and use chronological age. Some very premature babies (under 28 weeks) may take longer to catch up.
Common Myths About Baby Growth Charts
Myth: Higher percentiles are better.
Reality: The 5th percentile baby who stays there consistently is as healthy as the 95th percentile baby. Consistency matters, not the number.
Myth: My baby should gain weight steadily every week.
Reality: Weekly fluctuations are normal. Look at trends over months, not days or weeks.
Myth: Formula-fed babies should weigh more than breastfed babies.
Reality: WHO charts are based on breastfed babies, the biological norm. Formula-fed babies tracking higher than charts suggest they may be gaining too fast.
Myth: Chubby babies become obese adults.
Reality: Baby fat in the first year has no correlation with adult obesity. Toddler weight after age 2 begins to correlate weakly.
Tracking Growth at Home
Digital apps and baby scales allow home tracking between doctor visits. This is useful for:
- Babies with feeding challenges
- Premature babies catching up
- Peace of mind for anxious parents
- Monitoring the effectiveness of interventions
Weigh weekly at the same time, before feeding, in minimal clothing. Plot measurements monthly to see trends. Share data with your pediatrician at visits.
GrowthKit simplifies home tracking by automatically calculating percentiles, plotting curves, and showing growth velocity. Enter measurements in 30 seconds and see exactly where your baby falls on WHO and CDC charts.
Beyond the Numbers
Growth charts are screening tools, not diagnostic tests. They indicate when further evaluation may be needed but do not diagnose conditions.
Your pediatrician considers growth charts alongside:
- Physical examination
- Developmental milestones
- Feeding patterns
- Medical history
- Family genetics (tall parents have tall babies)
- Activity level
A baby at the 8th percentile with normal development, good feeding, and short parents is healthy. A baby at the 45th percentile who has dropped from the 75th needs assessment even though the current percentile looks normal.
The Bottom Line
Baby growth charts by age provide objective data about your child's physical development. The key insights: stay consistent with the curve your baby established in early months, watch all three measurements together, calculate growth velocity over time, and use WHO charts for ages 0-2.
Percentiles indicate where your baby falls compared to others. Trends over time indicate whether your baby is growing appropriately for their individual pattern. When patterns change suddenly or measurements are extreme, consult your pediatrician.
Track measurements systematically, plot them monthly, and bring data to appointments. This gives you and your doctor weeks of trend information rather than single point-in-time snapshots. Most importantly, remember that healthy babies come in all sizes, and the number matters far less than the consistency of the curve.
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