Baby Percentile Calculator
A baby percentile calculator compares your baby's weight, height, and head circumference to WHO growth standards. Enter your baby's measurements to see their baby growth percentile ranking and track healthy development with instant, accurate results.
Enter your baby's information for instant percentile calculation
Valid for ages 0-24 months (WHO standards)
Measure lying down for babies under 2 years
Measure around the widest part of head
Enter Measurements
Fill in your baby's information on the left to see instant percentile calculations and growth analysis based on WHO standards.
Weight
Height
Head
Baby percentiles compare your child's growth measurements to thousands of other babies of the same age and sex. Pediatricians use WHO (World Health Organization) growth charts to track whether your baby's weight, height, and head circumference fall within healthy ranges. Understanding your baby growth percentile helps parents monitor development over time.
Percentiles help doctors spot potential growth issues early. They're used at every well-baby checkup from birth through age 2. If your baby measures at the 40th baby growth percentile for weight, that means 40% of babies weigh less and 60% weigh more. This doesn't mean your baby is unhealthy. Most babies between the 3rd and 97th percentiles are growing normally.
Understanding your baby growth percentile helps you track growth patterns over time. A baby consistently at the 15th percentile who's gaining weight steadily is usually healthier than one jumping from 50th to 15th percentile in two months. Doctors look for consistent growth curves, not specific numbers.
WHO Growth Standards Percentile Ranges
| Percentile Range | Interpretation | What It Means |
|---|---|---|
| Below 3rd | May need evaluation | Only 3% of babies measure lower - discuss with pediatrician |
| 3rd-5th | Lower range | Monitor growth, ensure adequate nutrition |
| 5th-25th | Lower-average | Normal for many healthy babies, especially if consistent |
| 25th-75th | Average range | Most babies fall here - typical healthy growth |
| 75th-95th | Upper-average | Normal for many babies, monitor if rapid changes |
| 95th-97th | Higher range | Check for proportional development |
| Above 97th | May need evaluation | Only 3% of babies measure higher - consult pediatrician |
The WHO created these standards by studying 8,440 babies from six countries (Brazil, Ghana, India, Norway, Oman, USA). These babies were breastfed, healthy, and raised in optimal conditions. WHO standards represent how babies SHOULD grow when health needs are met, not just averages of all babies.
Parents often worry when their baby isn't at the 50th percentile. Don't. The 50th percentile is just the middle. Half of all healthy babies measure below it. What matters more is whether your baby follows their own growth curve consistently over time.
Using our baby percentile calculator takes less than two minutes. You'll need your baby's most recent measurements from a doctor visit or home measurement.
Before You Start, Gather:
- Baby's exact age in months (use decimals like 6.5 for 6½ months)
- Sex (growth patterns differ between boys and girls)
- Current weight (in pounds or kilograms)
- Current height/length (in inches or centimeters)
- Head circumference (in centimeters) - optional but recommended
Step-by-Step Instructions
- 1Select your baby's sex - Boys and girls have different growth curves. The WHO maintains separate standards because boys typically weigh slightly more and grow slightly faster.
- 2Enter age in months - Be precise. A 6-month-old baby and 6.5-month-old baby have different expected measurements. Our growth percentile calculator accepts ages from 0 to 24 months (WHO standards for infants and toddlers).
- 3Enter weight - Choose kilograms or pounds. For accuracy, weigh babies naked or in a clean diaper only. Home scales can vary by 1-2 ounces, so doctor office measurements are most reliable.
- 4Enter height/length - For babies under 2 years, measure lying down (called "length"). Use centimeters or inches. Measuring length at home is tricky. Babies wiggle. If measuring yourself, have someone help keep legs straight.
- 5Enter head circumference (optional) - Measure around the widest part of your baby's head, above the eyebrows and ears. This measurement tracks brain growth. Most parents skip this at home and rely on doctor measurements.
Pro Tips for Accurate Measurements
- Timing matters - Measure before feeding. Full bellies add weight and can affect length measurements when baby's uncomfortable.
- Consistency wins - Always use the same scale and measuring method. Don't compare home measurements to doctor office measurements directly.
- Clothes off - Remove all clothing except a clean diaper for weight. Even onesies add 2-4 ounces.
- Morning measurements - Babies are slightly longer in the morning (spine compresses during the day). Stick to one time for tracking.
Common Mistakes to Avoid
- ✗Comparing home scale to doctor scale (they often differ by 4-8 ounces)
- ✗Measuring length with baby's legs bent
- ✗Using measurements from different days to track changes
- ✗Measuring right after feeding or diaper change
Our baby percentile calculator shows results instantly. You'll see percentiles for weight, height, and head circumference (if entered). We'll show where your baby falls on WHO growth curves and explain what those numbers mean.
Baby percentile calculations compare your child's measurements to WHO growth standards based on thousands of healthy babies. The system uses statistical methods to determine where your baby falls on the growth curve.
How the Calculation Works
The WHO collected data from 8,440 babies across six countries over several years. For each age and sex, they recorded the 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, and 97th percentile values. Our growth percentile calculator uses interpolation to find the exact percentile for your baby's measurements.
The 50th percentile (median) represents the middle value. If your baby weighs at the 50th percentile, exactly half of babies weigh more and half weigh less. The child percentile calculator also shows a Z-score, which measures how many standard deviations your baby is from the median. A Z-score between -2 and +2 (roughly 3rd to 97th percentile) is considered normal.
Real Examples with Numbers
Example 1: 6-Month-Old Boy - 50th Percentile (Median)
A 6-month-old boy weighs 7.9 kg (17.4 lbs). This is exactly the 50th percentile for his age. That means 50% of 6-month-old boys weigh less and 50% weigh more. His Z-score is 0.0 (right at the median). This is perfectly average and healthy.
Note: If he weighed 7.5 kg at 3 months (also 50th percentile), he's following a consistent growth curve. This consistency matters more than the exact percentile.
Example 2: 12-Month-Old Girl - 15th Percentile
A 12-month-old girl measures 72.4 cm (28.5 inches) in length. This is the 15th percentile. That means 15% of girls her age are shorter and 85% are taller. Her Z-score is -1.04. This is normal if she's been consistently in the 10th-20th percentile range.
Why it's normal: If both parents are 5'4" or shorter, genes likely explain her smaller size. As long as she's growing steadily along her own curve, she's healthy.
Example 3: 9-Month-Old Boy - 95th Percentile
A 9-month-old boy weighs 10.5 kg (23.1 lbs). This is the 95th percentile. Only 5% of boys his age weigh more. His Z-score is +1.64. This is normal if he's consistently been in the 90th-97th percentile range and is developing proportionally.
Watch for: If his weight percentile is 95th but height is 40th, that's disproportionate. Doctor will check if it's just body type or if diet adjustments are needed.
Example 4: Edge Case - Percentile Drop
A baby was at the 60th percentile for weight at 4 months (6.4 kg) but dropped to 25th percentile at 6 months (7.0 kg). Even though 7.0 kg is technically "normal," the drop of 35 percentiles in two months is concerning. This needs medical evaluation.
Why it matters: Sudden drops often indicate feeding issues, illness, or other health concerns. Consistent growth patterns matter more than single measurements.
What Z-Scores Mean
- Z-score 0.0 = Exactly 50th percentile (median)
- Z-score +1.0 = About 84th percentile (one standard deviation above median)
- Z-score -1.0 = About 16th percentile (one standard deviation below median)
- Z-score +2.0 = About 97th percentile (two standard deviations above)
- Z-score -2.0 = About 3rd percentile (two standard deviations below)
Most healthy babies have Z-scores between -2.0 and +2.0. Values outside this range don't automatically mean something's wrong, but should be discussed with your pediatrician.
Your baby's percentile tells you where they stand compared to other babies, but it's not a grade or score. Here's how to understand what the numbers really mean for your child's health and development.
What Your Percentile Results Mean
Below 3rd Percentile
Your baby measures smaller than 97% of babies their age. Schedule a pediatrician visit soon. This could indicate feeding difficulties, medical conditions, or measurement errors. Most babies below 3rd percentile need evaluation, but some are just naturally small (especially if both parents are petite).
3rd-25th Percentile (Lower Range)
Your baby is smaller than average but likely healthy if growing consistently. Many perfectly healthy babies stay in this range. Watch for steady growth over time. If your baby's been at 15th percentile for three checkups, that's usually fine. If they dropped from 50th to 15th, discuss with your doctor.
25th-75th Percentile (Average Range)
Your baby falls right in the middle of the growth curve. Half of all babies are in this range. This is where most pediatricians expect to see healthy babies. Continue regular checkups and maintain current feeding practices. No concerns if growth stays consistent.
75th-95th Percentile (Upper Range)
Your baby is larger than average but likely healthy if proportional. Check that weight and height percentiles are similar (within 20-30 points). A baby at 85th percentile for both weight and height is well-proportioned. A baby at 90th for weight but 40th for height may need dietary review.
Above 95th Percentile
Your baby measures larger than 95% of babies their age. Discuss with your pediatrician to ensure proportional development. This could be genetics (tall/large parents often have large babies), overfeeding, or medical conditions. Most babies above 95th percentile are healthy, but deserve monitoring.
What Factors Affect Baby Growth Percentiles?
Many factors influence where your baby falls on growth charts. Understanding these helps you know what's normal versus concerning.
1. Genetics (Biggest Factor)
Parents' heights predict baby size. Two 5'4" parents usually have smaller babies (10th-30th percentile). Two 6'2" parents often have larger babies (70th-95th percentile). Check family growth patterns. If you were small as a baby but average as an adult, your baby may follow the same pattern.
Note: Genetics explains about 60-80% of height variation in healthy babies.
2. Nutrition and Feeding
Breastfed babies often gain weight slower than formula-fed babies after 3-4 months. This is normal. WHO standards are based on breastfed babies. Overfeeding can push percentiles up quickly. Underfeeding shows as percentile drops over 2-3 months. Solid food introduction (around 6 months) often causes temporary percentile shifts.
Red flag: Dropping 2+ percentile curves (from 50th to below 10th) in 2-3 months.
3. Prematurity and Birth Circumstances
Babies born early (before 37 weeks) often start at lower percentiles. They usually catch up by age 2-3. Use "corrected age" for preemies (subtract weeks early from current age). A baby born 6 weeks early at 6 months old should be measured as 4.5 months for accurate percentiles. Full-term babies with low birth weight may stay in lower percentiles their first year.
Corrected age matters until 2 years old for preemies.
4. Health Conditions
Reflux, allergies, tongue tie, and digestive issues affect weight gain. Chronic conditions (heart defects, metabolic disorders) may slow growth. Frequent illnesses in daycare can temporarily lower percentiles. Medications (like reflux meds) sometimes affect appetite. Most health-related growth issues show as falling percentiles over time, not staying at one low percentile.
Consult doctor if falling 2+ curves with illness symptoms.
5. Measurement Accuracy
Length measurements vary by 0.5-1 cm depending on who measures and baby's wiggling. Different scales show different weights (home vs doctor office can differ by 4-8 oz). Measuring after feeding adds weight. Measuring with clothes adds 2-4 oz. One "off" measurement doesn't mean growth problems. Look at trends over 3+ checkups, not single measurements.
Pro tip: Always measure same time of day, same conditions.
6. Ethnicity and Population
WHO standards represent global healthy babies, but genetic differences exist. Asian babies often track 5-10 percentiles lower than European babies. African babies sometimes track slightly higher. These are population averages, not rules for individuals. Your baby's growth pattern matters more than matching population averages. Some pediatricians use country-specific charts for better context.
WHO standards work well globally but aren't perfect for everyone.
When to Consult Your Pediatrician
- •Baby consistently below 3rd percentile or above 97th percentile
- •Percentile drops 2+ curves in 2-3 months (e.g., 60th to 20th)
- •Weight and height percentiles differ by more than 40 points (e.g., 90th weight, 30th height)
- •Baby not gaining weight for 2+ months (flat growth curve)
- •Head circumference growing too fast or too slow compared to body
- •Any concerns about feeding, development, or overall health
Trust your instincts. If something feels off about your baby's growth, talk to your doctor even if percentiles look "normal." Doctors evaluate growth alongside development milestones, feeding patterns, and overall health.
Baby percentile calculators are one way to track growth. Other methods provide different insights into your child's development and health.
| Method | Best For | Key Difference |
|---|---|---|
| WHO Growth Standards | Ages 0-24 months, breastfed babies | Shows how babies SHOULD grow under optimal conditions |
| CDC Growth Charts | Ages 2-20 years, US population | Shows how US children actually grow (includes formula-fed) |
| Weight-for-Height | Checking proportional growth | Compares weight to height (not age), spots over/underweight |
| BMI-for-Age | Children 2+ years | Body Mass Index adjusted for age, standard after toddler stage |
| Growth Velocity | Tracking rate of growth | Measures cm/month or kg/month gained, not just percentiles |
WHO vs CDC: Which to Use?
WHO charts are recommended for babies 0-24 months. They're based on healthy, breastfed babies from diverse countries. CDC charts work better for children 2+ years in the US because they reflect the actual population (including formula-fed babies and various ethnicities).
WHO percentiles run about 5-10 points lower for weight than CDC charts for formula-fed babies. This is normal. Don't switch between WHO and CDC when tracking your baby over time. Stick with one system for consistency.
When Weight-for-Height Matters More
Weight-for-height percentiles matter when weight and height percentiles are far apart. A baby at 90th percentile for weight but 40th for height is proportionally heavy. A baby at 20th for weight but 70th for height is proportionally thin.
Doctors use weight-for-height to identify overweight (above 85th percentile), obesity (above 95th percentile), or underweight (below 5th percentile) status regardless of overall size. It's more accurate than weight percentiles alone.
Growth Velocity: The Overlooked Measure
Growth velocity measures how fast your baby grows, not just where they are. A baby gaining 600g/month is growing faster than one gaining 400g/month, even if both are at the 40th percentile.
Expected growth velocity for babies:
- 0-3 months: 25-35 grams/day (175-245 g/week)
- 3-6 months: 15-21 grams/day (105-147 g/week)
- 6-12 months: 10-15 grams/day (70-105 g/week)
- 12-24 months: 5-10 grams/day (35-70 g/week)
Babies with low percentiles but good velocity are usually healthy. Babies with high percentiles but poor velocity need evaluation.
Expert answers to the most common questions parents ask about baby growth percentiles
What is a baby percentile calculator and how does it work?
A baby percentile calculator compares your baby's measurements (weight, height, head circumference) to WHO growth standards from 8,440 healthy babies worldwide. It shows where your baby ranks compared to others the same age and sex. If your baby is at the 60th baby growth percentile for weight, they weigh more than 60% of babies their age. The calculator uses your baby's exact age in months, sex, and measurements to find their percentile through statistical interpolation between standard data points.
What's a good percentile for a baby?
Any percentile between the 3rd and 97th is considered healthy and normal. About 94% of healthy babies fall in this range. There's no "best" baby growth percentile. The 50th percentile isn't better than the 25th or 75th. What matters most is consistent growth along your baby's own curve. A baby at the 20th percentile who stays there for six months is healthier than one who dropped from 60th to 20th in two months. Focus on trends, not individual numbers.
What does the 95th percentile mean for baby weight?
The 95th percentile means your baby weighs more than 95% of babies the same age and sex. Only 5% of babies weigh more. This doesn't automatically mean your baby is overweight or unhealthy. Many large babies at the 95th percentile are perfectly healthy, especially if both parents are tall or large. Check that weight and height percentiles are similar (within 20-30 points). A baby at 95th for both weight and height is proportional. A baby at 95th for weight but 40th for height needs evaluation for proper nutrition and growth.
Why is my baby's percentile different from the last visit?
Small changes (5-10 percentiles) between visits are completely normal. Babies don't grow perfectly steadily. They have growth spurts and slower periods. Measurement differences also play a role. Home scales can differ from doctor scales by 4-8 ounces. Length measurements vary by 0.5-1 cm depending on baby's position and who measures. Measuring after feeding adds weight. Worry only if percentiles drop 20+ points across 2-3 checkups or your baby shows other concerning symptoms.
What should I do if my baby is in a top percentile (90th-97th)?
Being in a top percentile isn't automatically concerning. Many healthy babies are naturally large, especially with tall parents. Check three things: (1) Are weight and height percentiles similar? A baby at 90th for both is proportional. (2) Is your baby consistently in this range? Stable high percentiles are usually fine. (3) Is development on track? If yes to all three, your baby is likely healthy. Discuss with your doctor if weight percentile is 30+ points higher than height, or if percentile jumped suddenly from 50th to 95th in 2-3 months.
Should I be worried if my baby is in a low percentile (3rd-10th)?
Not necessarily. Many healthy babies are naturally small, especially with petite parents. Low percentiles are concerning if: (1) your baby suddenly dropped from 50th to 10th percentile in 2-3 months, (2) they're not gaining weight for 2+ months, (3) they show signs of illness (lethargy, poor feeding, frequent vomiting), or (4) they're consistently below the 3rd percentile. If your baby has been at the 10th percentile for six months, is active, meeting milestones, and feeding well, they're likely just naturally small. Always discuss concerns with your pediatrician.
Do breastfed babies grow differently than formula-fed babies?
Yes, growth patterns differ significantly. Breastfed babies gain weight faster than formula-fed babies in the first 3 months. After 3-4 months, breastfed babies gain weight more slowly and often drop percentiles. A breastfed baby at 60th percentile at 3 months might be at 40th percentile by 9 months. This is completely normal and healthy. WHO growth charts are based on breastfed babies because they represent optimal growth. Formula-fed babies tend to be heavier after 6 months, which is why CDC charts (which include formula-fed babies) show higher weights.
Can I use this calculator for premature babies?
Yes, but use corrected age, not actual age. Corrected age accounts for how early your baby was born. Calculate it: subtract weeks premature from current age. Example: baby born 6 weeks early at 6 months old has corrected age of 4.5 months. Enter 4.5 months in the calculator for accurate percentiles. Use corrected age until about 24 months (2 years). After age 2, most preemies have caught up and you can use chronological age. Always discuss your premature baby's growth with a pediatrician familiar with preterm development.
Why do growth percentiles jump at the two-year mark?
You'll see jumps at age 2 for two reasons. First, measurement method changes: babies under 2 are measured lying down (length), while children 2+ are measured standing (height). Standing height is typically 1-2 cm shorter than lying length because gravity compresses the spine. Second, data source changes: WHO charts are used for 0-24 months, then CDC charts for 2+ years. These charts use different populations (WHO uses international breastfed babies; CDC uses US population including formula-fed). These shifts are normal and don't indicate growth problems.
How do I measure my baby's head circumference correctly?
Use a flexible measuring tape (not rigid ruler). Wrap it around the widest part of your baby's head: just above the eyebrows and ears, around the back where the head bulges most. The tape should be snug but not tight. Measure twice to verify accuracy. Common mistakes: measuring too high (above eyebrows), tape too loose, baby moving. Best time: when baby is calm or sleeping. Write down the measurement immediately. Head circumference grows fastest in the first 6 months (about 1.5 cm per month), then slows to 0.5 cm per month by age 1.
How often should I check my baby's growth percentiles?
Pediatricians typically measure at well-baby visits: 1, 2, 4, 6, 9, 12, 15, 18, and 24 months. You can check your baby growth percentile at home between visits, but don't obsess over every measurement. Check monthly at most. More frequent measuring leads to unnecessary worry about normal fluctuations. Focus on trends over 3-6 months, not week-to-week changes. If you're concerned about growth, measure weekly for 3-4 weeks and discuss the pattern with your doctor. Daily weighing is only needed for specific medical conditions under doctor guidance.
My baby is in different percentiles for weight, height, and head. Is that normal?
Usually yes. Many healthy babies have different percentiles for each measurement. What matters is proportionality. Weight and height should be within 20-30 percentiles of each other. Examples: 70th weight + 60th height = proportional (healthy). 90th weight + 30th height = disproportionate (needs evaluation). Head circumference can vary more independently but should grow steadily. A baby at 40th for head and 60th for weight is often fine. Red flags: weight percentile 40+ points higher than height, or head percentile not growing over 3+ months.
Do growth charts differ based on ethnicity?
The WHO charts are based on babies from 6 diverse countries (US, Brazil, Ghana, India, Norway, Oman) representing different ethnicities. Research shows that with proper healthcare and nutrition, healthy babies grow remarkably similarly across ethnicities during the first 5 years. Environmental factors and nutrition play a bigger role than genetics at this age. However, some population differences exist: Asian babies tend to track 5-10 percentiles lower than European babies, African babies sometimes track slightly higher. These are averages, not rules. Your baby's individual growth pattern matters more than matching ethnic averages.