Pregnancy Due Date Calculator

Pregnancy due dates use Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your LMP was January 1, your estimated due date is October 8. This assumes a 28-day cycle with ovulation on day 14 — adjustments are needed for longer or shorter cycles. A 35-day cycle means ovulation likely occurred around day 21, pushing the due date a week later. Only about 5% of babies arrive on their exact due date; most are born within a two-week window around it (38-42 weeks). Medical professionals count pregnancy in weeks rather than months because months vary in length. At 12 weeks you enter the second trimester, and at 28 weeks the third. This calculator shows your current week, trimester, days remaining, and key milestone dates. It also estimates conception date, which is typically two weeks after LMP. All dates are calculated locally — your pregnancy information stays completely private on your device.

Each week of pregnancy brings specific developmental milestones. By week 8, all major organs have begun forming. At week 12, the risk of miscarriage drops significantly (from about 10-15% in the first trimester to under 2%). Week 20 marks the halfway point and typically the anatomy scan ultrasound. By week 24, the fetus reaches viability — survival outside the womb becomes possible with intensive medical care. At week 37, the pregnancy is considered early term; full term is 39-40 weeks. Knowing these milestones helps you plan medical appointments: most providers schedule visits every 4 weeks until week 28, then every 2 weeks until week 36, then weekly until delivery. The glucose tolerance test typically happens around week 24-28, and the Group B strep test at weeks 36-37. This calculator maps out all these dates based on your LMP, giving you a complete timeline without needing to share sensitive medical information with any online service.