Plot baby weight, length, and head circumference on WHO growth charts by age. Enter values for instant results with step-by-step formulas.
Reviewed for accuracy by Rahul Singh, Health & Wellness Specialist
Reviewed for accuracy by Rahul Singh, Health & Wellness Specialist
Medical disclaimer:
This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.
Baby Growth Percentile Calculator
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Formula: Percentile = Normal CDF((measurement - median) / standard deviation) × 100
Your Result
Worked example — Weight: 50th percentile | Length: ~40th percentile — normal range
Formula
Percentile = Normal CDF((measurement - median) / standard deviation) × 100
Growth percentiles are calculated by comparing your baby's measurements to WHO growth standards. The z-score (how many standard deviations from the median) is converted to a percentile using the normal distribution. The 50th percentile represents the median (average) for the age and gender.
Worked Examples
Example 1: 6-Month-Old Boy
Problem:A 6-month-old boy weighs 7.9 kg (17.4 lbs) and is 67 cm (26.4 in) long.
Solution:Weight: 7.9 kg vs median 7.9 kg = ~50th percentile
Length: 67 cm vs median 67.6 cm = ~40th percentile
Result:Weight: 50th percentile | Length: ~40th percentile — normal range
Example 2: 12-Month-Old Girl
Problem:A 12-month-old girl weighs 10.2 kg and is 76 cm long.
Solution:Weight: 10.2 kg vs median 8.9 kg = ~81st percentile
Length: 76 cm vs median 74.0 cm = ~72nd percentile
Result:Weight: 81st percentile | Length: 72nd percentile — above average but normal
Frequently Asked Questions
What do growth percentiles mean?
Growth percentiles compare your baby's measurements to other children of the same age and sex. A 50th percentile means your baby is exactly average — 50% of children weigh more and 50% weigh less. The 25th percentile means 25% of children weigh less and 75% weigh more. Percentiles between the 3rd and 97th are generally considered normal. What matters most is that your child follows a consistent growth curve over time, not the specific percentile.
How often should I track my baby's growth?
The American Academy of Pediatrics recommends well-child visits (which include growth measurements) at: birth, 3-5 days, 1 month, 2 months, 4 months, 6 months, 9 months, 12 months, 15 months, 18 months, 24 months, 30 months, and annually from 3-21 years. Your pediatrician will plot measurements on growth charts at each visit. Between visits, tracking at home is optional but can help you notice trends.
When should I be concerned about growth?
Consult your pediatrician if: (1) Your child's percentile drops significantly (crossing two major percentile lines). (2) Measurements are below the 3rd or above the 97th percentile. (3) Weight-for-length is disproportionate. (4) Your child isn't meeting developmental milestones alongside growth. (5) You notice sudden changes in feeding patterns. Remember that growth spurts and temporary slowdowns are normal — the overall trend matters more than individual measurements.
What growth charts does Baby Growth Percentile Calculator use?
Baby Growth Percentile Calculator uses simplified data based on the World Health Organization (WHO) growth standards, which are recommended for children 0-2 years by the CDC. WHO standards describe how children should grow under optimal conditions (breastfed infants in non-smoking households across multiple countries). For children 2+, the CDC growth charts are typically used. Baby Growth Percentile Calculator provides estimates — always refer to your pediatrician's measurements for clinical decisions.
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