Pink Mom MathUltrasound Due Date Calculator
Adjust your due date based on ultrasound gestational age measurements. Compare with LMP dating per ACOG guidelines.
How the Ultrasound Due Date Calculator Works
This calculator derives an estimated due date (EDD) from ultrasound-measured gestational age. It reverses the standard gestational dating formula: back-calculates the LMP equivalent from the gestational age at the time of the ultrasound, then adds 280 days.
Formula: LMP equivalent = ultrasound date − (gestational weeks × 7 + gestational days). EDD = LMP equivalent + 280 days.
When you provide your LMP-based EDD, the calculator shows the discrepancy in days. Per ACOG Committee Opinion #700, a first-trimester discrepancy greater than 5-7 days warrants redating with the ultrasound measurement.
First-trimester accuracy: Crown-rump length (CRL) measurements before 14 weeks are accurate to within 5-7 days. Second and third trimester measurements carry greater uncertainty due to normal fetal size variation.
Frequently Asked Questions
Related Calculators
Due Date Calculator
Calculate your estimated due date from LMP, conception date, IVF transfer, or ultrasound. Supports twins.
Pregnancy Week Calculator
Find out exactly how far along you are in weeks and days with trimester milestone markers.
IVF Transfer Due Date Calculator
Calculate your estimated due date, LMP equivalent, and gestational age from your IVF embryo transfer date. Supports Day 3, Day 5, and Day 6 transfers.
Trimester Calculator
See your trimester stages with exact date ranges and key developmental milestones.
This calculator provides estimates for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider with questions about your health or your baby's health.
ACOG Guidelines