Pregnancy Due Date Calculator

A due date (estimated date of delivery, or EDD) gives you and your healthcare provider a timeline for prenatal care, testing, and preparation. While only about 4–5% of babies are born on their exact due date, it remains an essential planning tool throughout pregnancy.

How due dates are calculated: The standard method uses Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. For irregular cycles, the calculator adjusts by adding or subtracting the difference from 28 days.

LMP vs. conception dating: Gestational age is counted from the LMP, not conception. Since ovulation typically occurs around day 14, the baby is actually about 2 weeks younger than the gestational age. Conception date calculators add 266 days (38 weeks) instead.

When ultrasound is more accurate: First-trimester ultrasounds (before 14 weeks) are accurate to within 5–7 days. If the ultrasound date differs from the LMP date by more than 7 days, your provider will likely adjust your due date. Later ultrasounds are less accurate for dating.

IVF dating precision: IVF pregnancies have the most precise dating because the exact date of embryo transfer and embryo age are known. A day-5 blastocyst transfer is equivalent to being 2 weeks and 5 days pregnant (19 days past LMP).

Trimester overview: The first trimester (weeks 1–12) involves major organ development. The second trimester (weeks 13–26) is often the most comfortable, with rapid growth and movement. The third trimester (weeks 27–40) focuses on weight gain and lung maturation.

When to see your doctor: Schedule your first prenatal visit around weeks 6–8. Contact your provider immediately if you experience heavy bleeding, severe pain, high fever, or sudden swelling. Regular prenatal care is crucial for monitoring both your health and your baby's development.