Due Date Calculator
How Pregnancy Due Date Is Calculated
From conception vs last menstrual period
The average duration of pregnancy is 38 weeks (266 days) from conception. Predicting the pregnancy due date based on conception is the most accurate way to calculate one’s due date, but usually the date of conception is not known. Therefore, the due date is generally calculated from the first day of the last menstrual period (LMP). In this case, 2 weeks are added to the calculation giving a total of 40 weeks (280 days). This is based on the assumption that ovulation/conception occurs on cycle day 14 in the “average” 28 day menstrual cycle.
From ovulation
Calculating the due date from LMP (Last Menstrual Period) is subject to error since ovulation varies in its timing from the onset of menstruation among different women and from cycle to cycle. Many of Dr. Berger’s tubal reversal patients know their date of ovulation from using an ovulation predictor kit (OPK) or keeping a basal body temperature (BBT) chart. Calculating the pregnancy due date from ovulation is more accurate than from the last menstrual period.
This pregnancy due date calculator gives you the option of determining your due date from either the date of ovulation or the date of LMP. You can choose either of these dates in the calculator above.
