Rx Oasis’ free medically exact due date calculator and conception calculator calculates precisely your pregnancy due date. It will show you when your baby is due and when you conceived. Calculation of an accurate pregnancy due date is among the most important steps in pregnancy. 

Calculation of the best estimated due date (EDD) is based on the day of the date of ovulation and fertilization. The EDD can then be calculated by adding 266 days to the day of ovulation/fertilization.

What is the LMP Last Menstrual Period

The LMP or last menstrual period is the time of your regular bleeding. The first day of the LMP is the first day of your menstrual cycle. That is the date you enter when entering the LMP, the first day of the LMP.