Pregnancy due date & calendar

This calendar uses the first day of the last menstrual period (LMP), a usual cycle length of 20–45 whole days and an editable reference date. Defaults use your local calendar date at opening; they do not advance automatically overnight.

Model

Adjusted origin = LMP + cycle length − 28 days. Due date = origin + 280 days; estimated conception = origin + 14 days. Gestational age, remaining days and milestones all use this origin. Time since LMP is shown separately. This assumes cycle variation shifts ovulation; it is unreliable for irregular cycles and does not replace ultrasound dating.

Second trimester starts at 14 weeks 0 days, third at 28 weeks 0 days. Before the adjusted origin or from 42 weeks onward no trimester is assigned. Dates after the due date describe the calendar only and do not diagnose an ongoing pregnancy.

Windows

General references: anatomy ultrasound in weeks 18–22, diabetes screening in weeks 24–28, Tdap in weeks 27–36. The display includes each named week through day 6. Individual care can differ. Milestones are sorted by their starting date; no universal viability threshold is asserted.

Date calculations use calendar days, unaffected by daylight-saving time. Input years 1900–9998 and the 20–45-day cycle limits are software boundaries, not clinical validity claims. No conception-date input, clinical adjustment or state persistence is provided.