Calculate Expected Date of Delivery for Pregnancy
First Day of Last Menstrual Periodmm/dd/yyyy
Period CycleRange 20-45 days
Reference Date(mm/dd/yyyy)
Server Time7:58:46 AMAM/PM
Server Date6/24/2017(mm/dd/yyyy)
Note: Gestational age is calculated for the Reference date. Default is today's date. Change it to get gestational age on a specific date.

On an average, expected date of delivery is calculated by adding 280 days to the first day of the last menstural period for a cycle duration of 28 days. That is 10 lunar months. A lunar month is 28 days. It is also 40 weeks. Because the number of days in a standard Christian calender varies from 28 to 31, only an approximate value of 9 months and 7 days is given. Assuming 30-day months, then it would be 9 months and 10 days. First and second trimesters are each 13 weeks long (91 days). Anytime after that is third trimester.