Baby Percentile Calculator

Track your baby’s growth with the CareClinic Baby Percentile Calculator. Enter age, sex, weight, length, and head circumference to see how your child compares to international growth standards. Results are based on official WHO and CDC growth charts so you can spot patterns, answer common questions like “Is my baby’s weight normal,” and decide when to check in with your pediatrician.

Percentiles are comparisons, not a diagnosis. If you have concerns, speak with your healthcare provider.6

How to read percentiles at a glance

Example Meaning
Length at the 90th percentile Taller than 90 percent of same age peers
Weight at the 10th percentile Heavier than 10 percent of peers and lighter than 90 percent
Tracking along one curve over time Usually, more important than one single number

Frequently Asked Questions

What is a baby percentile calculator and how does it work

The CareClinic Baby Percentile Calculator uses your baby’s age, sex, and measurements to estimate percentiles for weight, length or height, and head circumference. It compares your child’s measurements with reference populations to show where they fall among peers. Calculations use WHO standards for infants and CDC references for older children, which are the most widely used growth tools worldwide.15

What percentile is my baby

Enter age, sex, weight, length or height, and head size. The calculator returns percentiles for each measurement so you can see how your baby compares to children of the same age and sex based on WHO and CDC data.15

What does a percentile mean for babies
  • Percentiles show comparison, not health status.
  • The 50th percentile is the median. It is not a target.
  • Trend over time matters more than one reading.6
Should I worry if my baby is in a low percentile
  • Not always. Some healthy children track low due to family body size.
  • Discuss with your clinician if numbers drop across curves or if there are feeding or development concerns.
  • Clinicians consider nutrition, illness, and family history, not percentile alone.
What if my baby is in a top percentile
  • High percentiles can be normal, especially for taller families.
  • Weight should be proportional to length or height.
  • For children age 2 and older, BMI for age percentiles help assess proportionality.78
How do I read a growth chart

Age is on the horizontal axis. Size is on the vertical axis. Curved lines show percentiles. The 50th curve is the median. Small shifts can be normal, especially in infancy. Large or persistent shifts may need review.6

Why do the curves seem to jump at about 2 years
  • Measurements change from recumbent length to standing height at about 24 months.
  • Many clinicians also transition from WHO standards to CDC references at this age.
  • Classification can change when charts or methods change, even if growth is steady.3
Do growth charts differ for breastfed and formula fed infants
  • Yes. Healthy breastfed infants often gain faster in the first few months, then more slowly for the rest of infancy.
  • WHO standards reflect growth of breastfed infants under optimal conditions.
  • CDC references include both feeding types from a U.S. population sample.24
Do growth charts differ based on ethnicity

WHO standards were built from healthy children in six countries with diverse backgrounds and living conditions. Under good nutrition and healthcare, early growth patterns are similar across populations, which is why these standards are used globally.19

What is the difference between WHO and CDC growth charts
Feature WHO Standards CDC References
Purpose How healthy children should grow under optimal conditions How U.S. children did grow over specific periods
Typical use Birth through 24 months Age 2 years and older
Population Multicountry, healthy, breastfed children U.S. national survey data across feeding types
Notes Shows faster early weight gain, then slower Widely used for school age tracking and BMI

Sources: WHO Child Growth Standards and CDC Growth Charts.156

Why are both WHO and CDC charts used
  • WHO is preferred for infants and toddlers to align with optimal growth patterns.
  • CDC is recommended for age 2 and older for continuity and BMI for age tracking.
  • Using both provides a complete view across early life into adolescence.27
How often should I check my baby’s growth

Medical visits commonly include growth checks at the following times. Your clinician may adjust based on your child’s needs.

Age Typical visit timing
Birth to 2 weeks Within 1 to 2 weeks after birth
2 to 6 months 2, 4, and 6 months
6 to 12 months 9 and 12 months
12 to 24 months 18 and 24 months
Age 2 and older Every year, or as advised

Reference example from Health Canada clinical guidance. Local guidance may vary.10

Can I use this calculator for premature babies
  • Yes, but adjust for gestational age until about age 2.
  • Corrected age gives a fairer comparison with peers born at term.
  • Clinicians can advise on which chart and adjustments to use.
How do I measure at home for accurate results
  • Weight: use the same scale, same time of day, minimal clothing.
  • Length: measure lying flat with legs gently straight, head against a firm surface.
  • Height after age 2: measure standing, heels together, back straight, no shoes.
  • Head size: wrap a flexible tape above eyebrows and ears, around the widest part of the back of the head. Take two or three readings and use the largest.
Which charts does CareClinic use and can I switch
  • CareClinic uses WHO standards for birth to 24 months and CDC references for age 2 and older to match public health recommendations.27
  • Clinicians may review both sets when interpretation is complex.
Will percentiles change after illness or a growth spurt
  • Short term illness can affect weight.
  • Temporary jumps or dips can occur in the first years.
  • What matters is the overall curve across several visits.
Does a high or low percentile predict adult height
  • Not precisely. Genetics and health over many years matter.
  • Percentiles are most useful for monitoring current growth and nutrition.
Tip: Save measurements in the CareClinic app to auto chart progress and share summaries at checkups.

References

  1. World Health Organization. Child Growth Standards and the Multicentre Growth Reference Study. Overview and methods. Accessed 2025. WHO site. MGRS page.
  2. Centers for Disease Control and Prevention. Use of WHO and CDC growth charts for children 0 to 59 months in the United States. MMWR Recommendations and Reports. 2010. CDC MMWR.
  3. Centers for Disease Control and Prevention. WHO Child Growth Standards training. Transition considerations. Updated 2024. CDC Training.
  4. Centers for Disease Control and Prevention. Using WHO growth standard charts. Breastfeeding related growth patterns. Updated 2024. CDC Training. See also PubMed record of the MMWR article: PubMed.
  5. Centers for Disease Control and Prevention. Growth Charts background and features. Background. Clinical charts.
  6. Centers for Disease Control and Prevention. Growth charts are tools to inform, not to diagnose. CDC Growth Charts page.
  7. Centers for Disease Control and Prevention. Child and Teen BMI calculator and categories. Updated 2024. BMI calculator. BMI categories.
  8. Centers for Disease Control and Prevention. Extended BMI for age growth charts for children with severe obesity. Extended BMI.
  9. World Health Organization. Methods and results of the WHO Child Growth Standards. 2006. PubMed abstract.
  10. Health Canada. Pediatric health assessment guidance including visit schedule. PDF.