Estimate your due date and track pregnancy milestones
Uses Naegele's rule to estimate your due date: add 280 days (40 weeks) from the first day of your last menstrual period, or 266 days from conception. Shows trimester breakdown and current progress. Note: only about 5% of babies are born on their exact due date.
Pregnancy due date calculation typically uses Naegele's rule: add 280 days (40 weeks) to the first day of the last menstrual period (LMP). While simple, this assumes a 28-day cycle with ovulation on day 14 — which varies significantly between women. Only about 5% of babies are born on their exact due date; most arrive within a two-week window around it. This calculator provides the estimated due date along with current gestational age, trimester information, and key milestones. It's meant as an informational tool — your healthcare provider will confirm dates with ultrasound measurements which are more accurate, especially in the first trimester.
Due dates are estimates — only about 5% of babies arrive on the exact date. About 80% are born within 2 weeks of the due date (between 38-42 weeks). First pregnancies tend to go slightly past the due date.
Add 7 days to the first day of your LMP, subtract 3 months, then add 1 year. This gives approximately 280 days (40 weeks) from LMP. It was developed by German obstetrician Franz Naegele in the early 1800s.
Yes — Naegele's rule assumes a 28-day cycle. If your cycle is longer (e.g., 35 days), ovulation likely occurred later, making your due date about a week later. This calculator can adjust for cycle length.
First trimester: weeks 1-12. Second trimester: weeks 13-26. Third trimester: weeks 27-40. Each trimester has distinct developmental milestones and maternal experiences.
Early ultrasound (before 13 weeks) can estimate gestational age within about 5 days by measuring the embryo. Your healthcare provider can establish dates through physical examination and imaging.