Estimated Fetal Weight Calculator

Estimated Fetal Weight Calculator

weeks
Enter gestational age in weeks (20-42 weeks)
mm
Measurement across the widest part of the fetal head
mm
Circumference around the fetal head
mm
Circumference around the fetal abdomen
mm
Length of the fetal thigh bone

Calculating estimated fetal weight…

Estimated Fetal Weight Results

Estimated Fetal Weight

0 g
Weight in pounds: 0 lbs
Weight in kilograms: 0.0 kg
Gestational age: 0 weeks
Percentile estimate: 50th percentile
Weight category: Normal

Formula Used:

Hadlock Formula

Weight Percentile Information

Your baby’s estimated weight falls within the normal range for the gestational age.

Important Disclaimer

This calculator provides an estimate only. Actual fetal weight may vary significantly. Ultrasound measurements can have a margin of error of ±10-20%. Always consult with your healthcare provider for proper interpretation of results and clinical decisions.

Understanding fetal growth is essential during pregnancy. The Estimated Fetal Weight Calculator is a practical tool designed to estimate a baby’s weight inside the womb using ultrasound measurements and gestational age. Whether you’re a parent seeking reassurance or a healthcare provider monitoring fetal development, this tool offers reliable and informative results in seconds.

What Is the Estimated Fetal Weight Calculator?

The Estimated Fetal Weight (EFW) Calculator helps estimate how much a fetus weighs based on standard biometric ultrasound measurements, including:

  • Gestational age (in weeks)
  • Biparietal diameter (BPD)
  • Head circumference (HC)
  • Abdominal circumference (AC)
  • Femur length (FL)

These values are used in scientifically validated formulas like Hadlock, Shepard, Warsof, and Campbell & Wilkin to compute the fetal weight in grams, pounds, and kilograms. The tool also provides percentile comparisons and categorizes the result based on fetal growth norms.

How to Use the Fetal Weight Calculator

Here’s a simple step-by-step guide to using the tool:

  1. Enter Gestational Age
    Input the number of weeks into pregnancy (must be between 20 and 42 weeks).
  2. Input Ultrasound Measurements
    Provide the following fetal biometric values:
    • Biparietal Diameter (BPD) – in mm
    • Head Circumference (HC) – in mm
    • Abdominal Circumference (AC) – in mm
    • Femur Length (FL) – in mm
  3. Choose a Calculation Method
    Select one of the four supported formulas:
    • Hadlock (default and most commonly used)
    • Shepard
    • Warsof
    • Campbell & Wilkin
  4. Click “Calculate”
    The calculator shows a progress bar for 3 seconds, simulating the analysis process.
  5. View Results
    The tool displays:
    • Estimated fetal weight in grams, pounds, and kilograms
    • Gestational age confirmation
    • Percentile ranking
    • Weight category (e.g., normal, small, or large for gestational age)
    • Formula used for calculation
  6. Copy or Share
    Easily copy results to your clipboard or share them via social media or message.

Example Calculation

Let’s say you’re 32 weeks into pregnancy and your ultrasound provides the following measurements:

  • BPD: 80 mm
  • HC: 280 mm
  • AC: 270 mm
  • FL: 60 mm
  • Method: Hadlock

After entering the values and clicking “Calculate,” the calculator estimates:

  • Fetal Weight: 1900 g
  • Weight in Pounds: 4.19 lbs
  • Weight in Kilograms: 1.900 kg
  • Percentile: 25th–75th
  • Category: Appropriate for Gestational Age
  • Formula: Hadlock Formula (BPD, HC, AC, FL)

This indicates healthy fetal development for 32 weeks.

Benefits of Using This Calculator

  • ✅ Accurate and Evidence-Based
    Uses established medical formulas validated by years of obstetric research.
  • ✅ User-Friendly Interface
    Simple layout, clear instructions, and responsive design.
  • ✅ Quick Estimation
    Results appear after a 3-second simulation, making the experience more engaging.
  • ✅ Multiple Calculation Methods
    Gives flexibility for different clinical preferences or available measurements.
  • ✅ Copy & Share Options
    Convenient buttons to share or save results for records or consultations.
  • ✅ Educational and Informative
    Displays percentile and weight category explanations for better understanding.

When to Use the Calculator

  • Prenatal Checkups: Estimate fetal weight during routine scans.
  • High-Risk Pregnancies: Track potential growth restrictions or macrosomia.
  • Personal Monitoring: Expecting parents can understand and follow fetal growth.
  • Remote Consultations: Share estimates with healthcare providers online.

Helpful Tips for Accurate Results

  • Always use recent and precise ultrasound measurements.
  • Double-check entries before clicking “Calculate.”
  • Use the Hadlock formula if unsure—it is the most widely accepted.
  • Remember: this is an estimate, not a substitute for professional medical advice.

FAQ – Estimated Fetal Weight Calculator

1. What is an estimated fetal weight?
It’s a calculated approximation of a baby’s weight inside the womb based on biometric ultrasound measurements.

2. How accurate is this calculator?
Estimates are based on clinical formulas with an average margin of error of ±10–20%.

3. Which formula is best to use?
The Hadlock formula is the most commonly used and generally preferred by healthcare professionals.

4. Is this calculator safe to use at home?
Yes, but it’s for informational purposes only. Always consult your healthcare provider for clinical interpretation.

5. What are the input requirements?
Gestational age (20–42 weeks) and measurements in millimeters for BPD, HC, AC, and FL.

6. What does percentile mean in fetal weight?
It shows how the estimated weight compares to population averages for the same gestational age.

7. What is considered small or large for gestational age?
Below the 10th percentile is small; above the 90th percentile is large.

8. Can I use this calculator in early pregnancy?
No. It’s designed for 20–42 weeks of gestation.

9. What units are used?
Millimeters for inputs; grams, kilograms, and pounds for outputs.

10. How often should I calculate fetal weight?
Only during routine ultrasounds or if advised by your doctor.

11. Will this calculator diagnose fetal growth issues?
No, it only estimates weight. Consult a healthcare professional for diagnosis.

12. Can I share the results with my doctor?
Yes. Use the “Share” button or copy the results and send them.

13. Does the tool store my data?
No. It performs all calculations locally on your device.

14. How is the percentile calculated?
Using internal benchmarks based on gestational age and weight ratio.

15. What does “Appropriate for Gestational Age” mean?
The estimated weight falls within the normal range for the current gestational age.

16. Is the calculator suitable for twins or multiples?
No. This version is designed for single-fetus pregnancies.

17. What if my measurements are outside the input limits?
Use the closest values within the range or consult a professional.

18. Can I reset the inputs?
Yes. Click the “Reset” button to clear all entries and start over.

19. How does the progress bar work?
It simulates processing for 3 seconds before displaying results for a better user experience.

20. Can the calculator predict birth weight?
No, it only estimates current fetal weight based on the latest measurements.

Conclusion

The Estimated Fetal Weight Calculator is an excellent companion during pregnancy for both expectant parents and healthcare providers. It transforms standard ultrasound metrics into meaningful insights about fetal growth and health. With user-friendly design, multiple formulas, and practical result interpretation, this tool is more than just a calculator—it’s a reassurance tool for the journey of parenthood.

For the most accurate monitoring, use this tool alongside your scheduled medical appointments and always consult your healthcare provider regarding the results.