Baby Growth Percentile Calculator
Estimate your baby's growth percentile based on gestational age, weight, and length compared to standard fetal growth charts.
Baby Measurements
Comparison to Averages
Growth Interpretation
Your baby's weight is around the average for this gestational age, indicating healthy growth.
How It Works
This calculator compares your baby’s weight, length, or head circumference to standardized growth charts (based on WHO and CDC fetal growth data) for their exact gestational age. The result is a percentile: for example, a 60th percentile means your baby is larger than 60% of babies at the same gestational age.
Percentiles are a snapshot, not a grade. A healthy baby can sit anywhere from the 10th to the 90th percentile consistently. What your doctor watches for is the trend over multiple visits, not a single number, since a baby steadily tracking along their own curve is usually a better sign than one measurement in isolation.
These figures are also population averages. Ethnicity, parental size, and individual variation all affect where a healthy baby falls, so always discuss your specific results with your provider rather than comparing against a single fixed target.
Frequently Asked Questions
How is fetal growth percentile calculated?
This calculator compares your baby’s estimated weight to standard fetal growth reference data for the same gestational age. The percentile indicates what percentage of babies at this stage weigh less than your baby. For example, the 60th percentile means your baby weighs more than 60% of babies at the same gestational age.
Where do baby weight and length measurements come from?
Fetal measurements are typically obtained from ultrasound scans. Weight is estimated using formulas that combine measurements of the head, abdomen, and femur. Length is measured from crown to rump (first trimester) or crown to heel (second/third trimester). Your healthcare provider will share these measurements with you.
What does it mean if my baby is in a low percentile?
A low percentile (below 10th) may indicate the baby is small for gestational age (SGA). This could be constitutional (small parents) or related to growth restriction. Your healthcare provider will monitor growth with serial ultrasounds. Many babies in lower percentiles are perfectly healthy.
What does it mean if my baby is in a high percentile?
A high percentile (above 90th) may indicate the baby is large for gestational age (LGA). This can be associated with genetic factors or conditions like gestational diabetes. Your healthcare provider will monitor growth and may recommend additional screening if concerns arise.
How accurate are fetal growth estimates?
Fetal weight estimates from ultrasound have an accuracy of about 10–15% in either direction. Growth charts are based on population averages and may not account for individual factors like ethnicity, maternal size, or genetic variation. Use this tool as a general reference, not a precise diagnostic measure.
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⚠️ Medical Disclaimer: This calculator provides estimates based on population growth reference data for informational purposes only. Fetal growth should be evaluated by a healthcare provider using clinical assessment and ultrasound. This tool is not a substitute for professional medical advice.
