Your doctor can work out your expected date of delivery (EDD) for you or there are many pregnancy calculators online that will estimate your due date at the click of a button. Alternatively if you want to work it out yourself, you can:
Find the date for your LMP, add one week, subtract three months and then add one year.
For instance, for a LMP of 30th May it works like this:
30th May + one week = 6th June
6th June – three months = 6th March
6th March 2011 + one year = 6th March 2012
The Lunar Pregnancy Calculator
That doesn’t mean the pregnancy symptoms have driven you mad. It is another method of calculating how pregnant you are, based upon the conception date as the start of pregnancy, which is actually more accurate. The method, however, is not used in the United States. The lunar method is mainly used in Far Eastern countries.
https://www.empowher.com/pregnancy/content/estimating-your-due-date