How To Find The Exact Due Date?

If you are asking about due date of delivery of a baby then good source is ultrasound that can tell about current gestational age of the baby and expected date of delivery. Gestation in primates including humans can be of 9 months or 40 weeks. Exact date of delivery is some what difficult to calculate because it depends upon conception date.

After conceiving, a woman needs 38 more weeks to complete gestation. One common way to calculate expected date of delivery is to add 280 days or 9 months or 40 weeks in the first day of last menstrual period and this is most accurate method that is used in clinical practice.

Going to the doctor. They can tell you the approx date