Pregnancy Due Date Calculator - Free Online Due Date Estimator

Finding out your estimated due date is one of the most exciting moments of pregnancy. Our free pregnancy due date calculator uses Naegele's Rule, the same method obstetricians and midwives have relied on for over a century, to estimate when your baby is likely to arrive. By entering the first day of your last menstrual period (LMP) and your average cycle length, you receive a personalized due date along with key pregnancy milestones. Naegele's Rule works by adding 280 days (40 weeks) to the first day of your last menstrual period. Because not every woman has a textbook 28-day cycle, our calculator also adjusts for your individual cycle length. If your cycles are longer or shorter than average, the due date shifts accordingly for a more accurate estimate. The calculator then determines how far along you are in weeks and days, identifies your current trimester, and shows when each trimester ends. It is important to understand that a due date is an estimate, not a guarantee. Research shows that only about 5% of babies are born on their actual due date. Most healthy pregnancies last between 38 and 42 weeks, and a range of factors including genetics, the number of previous pregnancies, and maternal health can influence when labor begins naturally. This calculator is intended for informational and planning purposes only. It should not replace prenatal care or guidance from your healthcare provider. Your obstetrician or midwife may adjust your due date based on early ultrasound measurements, which can be more precise than LMP-based calculations, particularly if your cycles are irregular. Always attend your scheduled prenatal appointments for the most accurate pregnancy timeline.