Pregnancy Due Date Calculator

Calculate your estimated due date, current gestational week, trimester, and key pregnancy milestones.

This calculator dates a pregnancy and, unlike a simple due-date tool, also reports how far along you are right now. The due date comes from the standard rules: 280 days from the first day of your last menstrual period (Naegele's rule), or 266 days from a known conception date — two anchors that agree whenever ovulation falls on day 14 of the cycle. Gestational age is then measured against today: weeks and days since the start date, with a 14-day adjustment under the conception method because medical convention counts pregnancy weeks from the last period, not from fertilization. That convention is worth understanding — under the conception method your "week" runs about two ahead of the actual time since fertilization. Trimester labels switch at weeks 14 and 28, Progress is weeks out of 40 capped at 100, and Days Remaining floors at zero, so once a due date passes the tool saturates rather than reporting a negative countdown. The milestone dates are fixed offsets from the start: first trimester ends at 13 weeks, viability is marked at 24 weeks, and the second trimester ends at 27. None of this accounts for cycle irregularity, early-ultrasound redating (which trumps calendar math clinically), or the fact that a due date is the center of a normal range, not a deadline.