Due Date Calculator – Pregnancy Calendar Tracker. Your due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (assuming a 28 day cycle). Additionally, it is helpful to determine how long you have been pregnant, in.

Ovulation itself typically lasts for 12 to 24 hours. The due date calculator estimates the delivery date of a pregnant woman based on her last menstrual period (lmp), ultrasound, conception date, or ivf transfer date.