how to calculate expected delivery date
The average length of a pregnancy is 40 weeks, or 280 days, from the first day of the last normal menstrual period. Calculating the due date, or expected date of delivery, for a pregnancy is quite simple, then, if you know that date. Simply add nine months and seven days to the date, and you've got your pregnancy due date. Here's an example of how it works: Say the first day of the last normal menstrual period was January 1st. Add seven days to that number, and you get the number 8. Add nine months, and you get October.