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Due date by ultrasound
Estimate your due date from an ultrasound's gestational age measurement.
Estimate, not a diagnosis. This tool gives an educational estimate based on the numbers you enter. It cannot account for your individual health history — consult a healthcare professional for anything clinical.
Notes
Ultrasound dating is typically more accurate than LMP-based dating in early pregnancy. Accuracy varies by gestational age and measurement type — early first-trimester crown-rump length (CRL) is the most precise.
Limitations
Later scans have wider margins of error. Your care provider's dating should take precedence over this estimate.
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Frequently asked questions
Why is ultrasound dating more accurate than last-period dating?
Ultrasound measures the actual size of the fetus, which is a direct physical measurement, rather than assuming a standard cycle length and ovulation timing. It is especially useful when your last period date is uncertain or your cycles are irregular.
Which ultrasound measurement is most accurate for dating?
Crown-rump length (CRL) taken in the first trimester is considered the most precise dating measurement. Measurements from later scans have progressively wider margins of error.
Should I use my ultrasound date or my last-period date?
Your care provider’s official dating, usually based on an early ultrasound when available, should take precedence over any self-calculated estimate, including this one.