Baby Weight Percentiles: Birth to 24 Months
WHO weight-for-age charts compare an infant with children of the same age and sex. Use the trend alongside feeding, birth history and other measurements. A percentile is a reference position, not a feeding target or a diagnosis.
Updated 15 October 2026 · Educational guidance
What weight-for-age can show
The WHO standard provides separate charts for boys and girls. A baby at the 50th percentile is near the middle of that reference distribution. There is no requirement for every baby to move toward the middle, and a higher number is not automatically healthier.
Weight-for-age does not measure body composition or assess weight relative to length. A clinician may consider length, head circumference and other growth information before interpreting the result.
Keep a useful measurement record
Record the date, exact age and weight in kilograms. Use a suitable infant scale and follow the clinic's measurement instructions. Clothes, a wet diaper and differences between scales can affect comparisons. If the number looks unexpected, ask the clinic to repeat it.
Bring the growth card to follow-up visits. Keep the measurement method consistent where possible and tell the clinician about recent illness or feeding changes. Do not repeatedly weigh a baby solely to chase a particular percentile.
Birth history changes the interpretation
Prematurity and medical history can affect which chart and age convention are appropriate. Ask the paediatrician whether corrected age should be used; this guide does not calculate a personalised prematurity correction.
Around the transition from infant to child charts, a plotted position can change because the reference and measurement method change. Keep that transition in the record rather than interpreting it as an immediate loss of growth.
Discuss concerns promptly
A fall across the pattern of previous measurements deserves a clinical discussion, particularly with feeding difficulties or illness. Seek urgent care for a baby who appears seriously unwell; do not wait for a percentile calculation. Never change formula concentration or start supplements based on the chart alone.
Frequently asked questions
Should I try to reach the 50th percentile?
No. Ask about your baby's own growth pattern and feeding needs rather than a target percentile.
Can weight alone diagnose undernutrition?
No. Weight-for-age is one part of assessment; other measurements and clinical history are needed.
What if my baby was born early?
Ask the paediatrician which reference and age correction to use before interpreting the result.
Sources
Educational information only. A calculator or a guide cannot diagnose a condition. Discuss concerning symptoms or results with a qualified healthcare professional.