Due Date Calculator — When Is My Baby Due?
Calculate your estimated due date using your last menstrual period, conception date, or IVF transfer date. Includes current trimester and key milestone dates.
Enter the date that matches your selected method above.
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Frequently asked questions
How accurate is Naegele's Rule for calculating due dates?
Naegele's Rule (LMP + 280 days) is a solid first estimate, but a first-trimester ultrasound crown-rump length (CRL) measurement at 7–12 weeks is more accurate. Studies show births cluster around 39–41 weeks; the most common birth week is 39–40. First-time mothers tend to go slightly past their due date; second-time mothers tend to deliver a bit earlier. Your OB will use the LMP estimate and first ultrasound together to establish your confirmed EDD.
What if I don't know my last menstrual period?
A first-trimester ultrasound (7–12 weeks) can establish gestational age from the fetal crown-rump length (CRL) with high precision. If ultrasound dating differs from LMP dating by more than 5–7 days in the first trimester, the ultrasound date takes precedence. Second-trimester biometry is less accurate for dating. If you're uncertain about your LMP, use the conception date input if you have a better estimate.
What is 'full term' in pregnancy?
ACOG defines full term as 39 weeks 0 days through 40 weeks 6 days. Before 37 weeks is preterm; 37–38 weeks 6 days is early term; 41+ weeks is late term; 42+ weeks is post-term. Elective deliveries before 39 weeks without medical indication are generally discouraged — babies born at 37–38 weeks have higher rates of respiratory, feeding, and developmental challenges than those born at 39+ weeks.