Due Date Calculator

Only about 4% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the due date. The calculation assumes a 28-day cycle and ovulation on day 14.

Naegele's rule is a standard method to estimate the due date: add 280 days (40 weeks) to the first day of the last menstrual period. It was developed by Dr. Franz Karl Naegele in the 19th century.

Yes. If your cycle is longer than 28 days, you ovulate later and your due date is later. If shorter, you ovulate earlier. This calculator adjusts for your cycle length.

A baby is considered full term at 39-40 weeks. Early term is 37-38 weeks, late term is 41 weeks, and post term is 42 weeks or beyond.

Fetal viability (the point at which a baby can survive outside the womb with medical support) is generally considered to be around 24 weeks of pregnancy, though outcomes improve significantly after 28 weeks.

For IVF pregnancies, the due date is calculated by adding 266 days to the egg retrieval date. This is equivalent to adding 280 days to an estimated LMP that is 14 days before retrieval.