Pregnancy Calendar and Due Date Calculator

A pregnancy calendar and due date calculator estimates a due date and the current pregnancy week from any of five starting points: the first day of the last menstrual period, a known conception date, a provider-given due date, an ultrasound date with gestational age, or an IVF transfer date. The resulting timeline covers prenatal visits, maternity leave planning, and other milestones tied to specific weeks.

• Five calculation methods produce the same set of results: Last Period, Conception Date, Due Date, Ultrasound Date, or IVF Transfer Date.
• The Last Period method also needs an average cycle length, which defaults to 28 days when the actual cycle length is unknown.
• Results include the estimated due date, current pregnancy week, estimated conception date, and progress percentage.
• A Pregnancy Milestones Timeline shows trimester windows and important developmental points.
• Changing an input, such as cycle length or an ultrasound finding, recalculates the estimate for comparison against the original scenario.

• Last Period (LMP): Add 280 days to LMP and adjust for cycle length.
• Conception Date: Add 266 days to the conception date.
• Known Due Date: Subtract 280 days to estimate LMP and backfill the timeline.
• Ultrasound Date: Add the remaining days to reach 280 days using the reported gestational age.
• IVF Transfer Date: Add 266 days for day-0, 264 days for day-3, or 261 days for day-5 transfers.

These are standard obstetric conventions. A typical gestation runs 40 weeks measured from LMP, with 38 weeks from conception as a common reference point.

• LMP Method: Due Date = LMP + 280 days − (28 − cycle length).
• Conception Method: Due Date = Conception Date + 266 days.
• Known Due Date: LMP = Due Date − 280 days.
• Ultrasound Method: Due Date = Ultrasound Date + (280 − Gestational Age in days).
• IVF Method: Due Date = Transfer Date + (266 − Embryo Age in days).

• Prenatal care scheduling: visits, screenings, and classes timed to trimester windows.
• Leave planning: workplace notifications, maternity or parental leave, and childcare setup timed to the estimated due date.
• Home readiness: target dates for a hospital bag, nursery setup, and car seat installation.
• Progress tracking: weeks and milestones mapped to growth stages and upcoming appointments.
• IVF timelines: transfer specifics mapped to due date expectations and follow-up care.

An LMP of March 1 with a 30-day cycle produces a slightly later due date than the same LMP on a 28-day cycle, since the formula adjusts for cycle length. A known conception date cross-checks against the conception date the LMP method backs out. An ultrasound date carrying 12.5 weeks of gestational age shifts the projected due date to match the fetal measurement rather than the menstrual history. An IVF day-5 transfer date factors in the embryo's age at transfer rather than treating it as day zero. Changing any input updates the current week and the milestone windows to match.

The output reports four figures: Estimated Due Date, Current Pregnancy Week, Estimated Conception Date, and Pregnancy Progress. The milestone timeline marks trimester ranges and checkpoints such as the full-term window. These dates are estimates; they shift with cycle length, ultrasound adjustments, and clinical guidance.

How accurate is the due date? Most pregnancies do not deliver exactly on the due date. Providers often discuss a full-term window rather than a single day. Why does cycle length matter? Longer or shorter cycles shift ovulation timing, which changes the projected conception date and due date. Which method should I use? The method to use is whichever one reflects the most reliable available information; ultrasound dating in the first trimester often refines estimates. Can this be used after IVF? Yes. The IVF Transfer Date method accounts for the embryo's age at transfer, whether day-0, day-3, or day-5.

This tool is for general informational purposes only and is not intended to provide medical advice. It does not consider individual health conditions and should not be used as a substitute for professional medical advice, diagnosis, or treatment.

Always seek guidance from a qualified healthcare provider with any questions you may have regarding your health. Do not disregard medical advice or delay seeking care based on information provided by this tool.

If you believe you may be experiencing a medical emergency, contact your doctor or call emergency services immediately.