Estimated Fetal Weight (EFW) Calculator
Normal fetal growth is important not only for a healthy pregnancy, but also for ensuring health and well-being throughout childhood and adolescence. The NICHD Fetal Growth Study, started in 2009, aims to set evidence-based standards for normal fetal growth and size for each stage of pregnancy. Learn more about the Study's findings.
This calculator uses data from the NICHD Fetal Growth Study to calculate Estimated Fetal Weight (EFW) for a singleton (one) fetus between 10 weeks 0 days and 41 weeks 6 days of pregnancy. Depending on the ultrasound measurements included, the calculator can provide four estimates of EFW percentiles.
Unlike other estimation methods, the NICHD EFW calculator results take the mother's self-identified race/ethnicity into account, a critical issue following the Study’s findings that EFW percentiles could be incorrect for non-white fetuses if a single growth standard is used.
Users should keep in mind that factors beyond those used to calculate EFW may affect an infant's birth weight. Definitions of the measurements used for the EFW calculator are available, as are ranges for the measurements (spreadsheet linked below). To estimate fetal weight, enter information below, and select the “Submit” button. After the Submit button is clicked, information for EFW will appear below it. You may need to scroll down to view the results table. If the input is not within the expected range, the results will be displayed based on the values of the inputted data.
Percentile Range Spreadsheet
Fetal Growth Calculator Percentile Range (PDF 1.55 MB)
The spreadsheet is used to help users confirm the results. So values inputted below the 3rd percentile or above the 97th percentile will appear as <3% and >97%, respectively, in the calculation results.
For example, if a user enters a Gestational Age (GA) of 10 weeks and 2 days, a Race of White, and an Abdominal Circumference (AC) of 31, then the results will be <3%. If the User enters 34.46 in the AC field instead, then the result will be 10%.