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Ultrasound Due Date Calculator
Calculate your estimated due date based on your ultrasound scan measurements.
Enter Scan Details
Select the date of your ultrasound scan.
Enter the gestational age as shown on your ultrasound report.
How This Calculator Works
The ultrasound-based due date is often more accurate than LMP-based calculations:
- Due date = Scan date + (280 - gestational age in days)
- First trimester ultrasounds are the most accurate (within 5-7 days)
- Your doctor may adjust the due date if it differs significantly from LMP-based estimates
Ultrasound Accuracy by Trimester
Ultrasound dating accuracy varies by trimester:
- First trimester (6-13 weeks): Accurate within 5-7 days
- Second trimester (14-27 weeks): Accurate within 10-14 days
- Third trimester (28+ weeks): Accurate within 21-30 days
Medical Disclaimer
- This calculator provides an estimate only and is not a substitute for professional medical advice.
- Your OB-GYN will confirm your due date based on multiple factors including ultrasound, LMP, and clinical assessment.
- Only about 5% of babies are born on their exact due date. Most arrive within a 2-week window.
100% private. This calculator runs entirely in your browser. Your dates are never sent to a server or stored.
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