Calculating Due Date

A typical pregnancy lasts, on average, 280 days, or 40 weeks—starting with the first day of the last normal menstrual period as day 1. An estimated due date can be calculated by following steps 1 through 3:

1. First, determine the first day of your last menstrual period.

2. Next, count back 3 calendar months from that date.

3. Lastly, add 1 year and 7 days to that date.
   

Calculating a Due Date | Johns Hopkins Medicine www.hopkinsmedicine.org/health/wellness-and-prevention/calculating-a-due-date