Fetal Weight Calculator

The Fetal Weight Calculator estimates a baby's weight in the womb using ultrasound measurements — a key tool for tracking fetal growth during pregnancy. Enter your gestational age (weeks and days) along with four ultrasound measurements: Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL). You'll get the Estimated Fetal Weight in grams, plus the weight percentile and weight category for your stage of pregnancy.

Complete weeks of pregnancy

Additional days (0-6)

mm

Measurement across the fetal head

mm

Circumference around the fetal head

mm

Circumference around the fetal abdomen

mm

Length of the fetal thigh bone

Results

Estimated Fetal Weight

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Weight Percentile

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Total Gestational Age

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Weight Category

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Frequently Asked Questions

How accurate is the fetal weight calculator?

Fetal weight calculators typically have an accuracy of ±10-15% of actual birth weight. The accuracy depends on the quality of ultrasound measurements and gestational age.

What ultrasound measurements are needed for fetal weight estimation?

The calculator uses four key measurements: Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL). These measurements help estimate fetal size and development.

What do the percentiles mean in fetal weight estimation?

Percentiles compare your baby's estimated weight to other babies at the same gestational age. The 50th percentile is average, while below 10th percentile may indicate small for gestational age (SGA).

When is fetal weight estimation typically performed?

Fetal weight estimation is commonly done during routine ultrasounds, especially in the second and third trimesters (20-40 weeks) to monitor fetal growth and development.

Can fetal weight calculators predict birth weight exactly?

No calculator can predict exact birth weight. Factors like maternal health, genetics, delivery timing, and measurement accuracy all influence the final birth weight.

What should I do if the estimated fetal weight seems concerning?

If results show very high or low percentiles, discuss with your healthcare provider. They may recommend additional monitoring, nutritional counseling, or further testing.

Are there different formulas for calculating fetal weight?

Yes, several formulas exist including Hadlock, Shepard, and Warsof methods. This calculator uses the widely accepted Hadlock formula which incorporates all four biometric measurements.