About this calculator
This calculator estimates an expected due date from an ultrasound date and the gestational age listed on that ultrasound report.
Due dates are estimates. Your obstetric clinician’s recorded EDD should take priority, especially when there are multiple scans, irregular cycles, IVF dating, or medical complications.
Estimates EDD by adding the remaining days to 40 weeks: ultrasound date + (280 − gestational age in days). ACOG notes first-trimester ultrasound is the most accurate method to establish or confirm gestational age.
Activated — obstetric dating estimate
Ultrasound dating accuracy depends on gestational age at scan, measurement quality, multiple pregnancy, fetal growth concerns, and local obstetric guidance.
Formula and method
Estimated due date = ultrasound date + (280 days − gestational age in days on the scan). Gestational age in days = weeks × 7 + days.
Limitations and when not to rely on this result
- Ultrasound dating accuracy depends on gestational age at scan, measurement quality, multiple pregnancy, fetal growth concerns, and local obstetric guidance.
- Clinician-documented estimated due date should supersede this calculator.
- Do not use for urgent pregnancy symptoms, viability decisions, or growth assessment.
Frequently asked questions
How do I use this ultrasound due date calculator? +
Enter the date of the ultrasound and the gestational age written on the report. The calculator adds the remaining days to 40 weeks.
Is ultrasound more accurate than LMP? +
ACOG notes that first-trimester ultrasound is the most accurate method to establish or confirm gestational age. Later scans are generally less precise for dating.
Can this replace my official due date? +
No. Use the EDD documented by your obstetric clinician, especially if the date has been confirmed or revised in your medical record.
Why is the result different from my app? +
Apps may use LMP, conception date, IVF date, or a different scan. Clinical dating rules prioritize the best available obstetric estimate.
What if my scan was late in pregnancy? +
Third-trimester dating is less precise. Ask your clinician which EDD should be used for care decisions.