Calculate your estimated due date and track your pregnancy timeline. Enter the first day of your last menstrual period to see your due date, current week, and key trimester milestones.
Pregnancy is dated from the first day of your last menstrual period (LMP), not from conception. Using Naegele's rule — the standard method used by obstetricians — 280 days (40 weeks) are added to the LMP date to estimate the due date. Conception typically occurs around day 14 of a 28-day cycle, so the actual gestational age of the baby is about two weeks less than the pregnancy dating. Only about 5% of babies arrive on the exact due date, so it is best thought of as the midpoint of a likely delivery window spanning 38 to 42 weeks.
This calculator uses Naegele's rule, the standard method used by doctors. It adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation occurring on day 14.
Only about 5% of babies arrive on their exact due date. Most are born within a two-week window around the due date — between 38 and 42 weeks is considered full term. An ultrasound in the first trimester can provide a more accurate estimate.
The first trimester covers weeks 1–12 and involves major organ development. The second trimester (weeks 13–26) is when growth accelerates and movement becomes noticeable. The third trimester (weeks 27–40) focuses on weight gain and final development before birth.
If your cycle is longer than 28 days, your actual due date may be a few days later than calculated. If shorter, it may be earlier. For cycles that differ significantly from 28 days, your doctor may adjust the due date based on an early ultrasound measurement.
Schedule your first prenatal visit between 6 and 8 weeks of pregnancy. A first-trimester ultrasound (before 14 weeks) provides the most accurate dating and can confirm or adjust the due date calculated from your last period.
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