Estimate fetal weight using ultrasound measurements (BPD, AC, FL) with multiple standard obstetric formulas.
The length of the widest part between the left and right sides of the fetal head
The circumference of the fetal abdomen
The length of the fetal thigh bone
Chinese obstetric guidelines recommended formula: Y = 1.07×BPD³ + 0.3×AC²×FL, applicable to most gestational weeks.
Enter ultrasound data to start calculation
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When looking at an ultrasound report, many expectant parents wonder how to estimate their baby's weight from measurements like biparietal diameter (BPD) and abdominal circumference (AC). This tool quickly calculates the estimated fetal weight by taking ultrasound measurements (BPD, AC, femur length, etc.) and applying medically validated estimation formulas. Its core function is to process fetal biometric indicators in centimeters (cm) and convert them into an estimated weight in grams (g) using specific mathematical formulas (such as Hadlock, Shepard, etc.), providing a reference for pregnancy nutrition and delivery planning.
Q: Which fetal weight calculation formula is the most accurate?
There is no absolute "most accurate" formula. Different formulas (like Hadlock and Shepard) have different focuses and are suitable for different gestational weeks, leading to normal variations in results. It is generally recommended to use the formula commonly preferred by your clinician or recommended by your local obstetric guidelines as the primary reference.
Q: If I input numbers like 9.5, 33, 36.5, and 7.6, roughly how heavy will the estimate be?
Approximately 3000 grams (about 6.6 lbs). This is a typical estimation example based on standard formulas. Actual results will fluctuate slightly depending on the specific formula chosen.
The results provided by this tool are medical estimates only and cannot replace a professional diagnosis by an obstetrician. Please ensure the input data comes from a recent, official ultrasound report and that the values are accurate. Calculation results have a certain margin of error, especially for extreme gestational ages or special fetal conditions. This tool does not store or upload any of your input data, so you can use it with confidence; however, avoid entering sensitive personal medical information on public computers.
For clinical professionals or users who want a deeper understanding, we recommend learning the applicable scenarios for different formulas. For example, the Hadlock formula integrates multiple parameters like head circumference (HC), abdominal circumference (AC), and femur length (FL), and is considered relatively stable in the second and third trimesters. The Shepard formula, on the other hand, relies primarily on BPD and AC. In practice, if measurement data (like AC) is skewed due to fetal position, it will directly affect the calculation result. Therefore, results should be interpreted in conjunction with ultrasound image quality and clinical context. Typical input/output example: Input Biparietal Diameter (BPD) 9.5 cm, Abdominal Circumference (AC) 36.5 cm, Femur Length (FL) 7.6 cm. Using the standard formula, the estimated fetal weight output is approximately 3000 g.
