A Parents Pregnancy Guide to Pregnancy Calculator

Pregnancy Calculator    

Pregnancy Calculator

How it Works
The common method for calculating your due date is to add 280 days to the first day of your last menstrual period, or LMP. The 280 days accounts for the typical 266-day gestation period plus and extra 14 days, to estimate when you would have most likely been ovulating. This method assumes that you began ovulating exactly 14 days after the beginning of your period and fertilization took place on that day.

The prediction can be made much more accurate by keeping track of your basal body temperature, in order to know exactly when you were ovulating, had intercourse, and became pregnant. If you knew this day exactly, you could simply add on the typical 266-day gestation period, giving you your due date.

Our pregnancy calculator below is more accurate than most, as it allows you to input the average length of your menstrual cycles and the average luteal phase length, if you have that information available.

Last Menstrual Period:        
                              (MM/DD/YYYY format)

Average Length of Cycles:      (22 to 45)
                              (defaults to 28)

Average Luteal Phase Length:   (9 to 16)
                              (defaults to 14)



Estimated Conception:         
Estimated Due Date:           
Estimated Fetal Age: