Pregnancy Due Date Calculator

A pregnancy due date is usually estimated as 280 days (40 weeks) after the first day of your last menstrual period, known as the LMP. If your last period started on January 1, 2026, the estimated due date is October 8, 2026. This calculator works it out from your LMP or from a known conception date.

With the LMP method, the tool assumes a 28-day cycle. Enter your usual cycle length, from 20 to 45 days, and it moves the date by the difference. A 32-day cycle adds 4 days, and a 25-day cycle takes 3 away. With a known conception date, it adds 266 days (38 weeks).

Along with the due date, you see the estimated conception date and the dates your first and second trimesters end. If the date you enter is in the past, it also shows how far along you are in weeks and days, the trimester and the days left. Pregnancy weeks are counted from the LMP, about two weeks before conception. So at conception you are already counted as two weeks pregnant.

A due date is an estimate, not a deadline. Only a small share of babies arrive on the exact day, and many come in the weeks around it. Your doctor or midwife may change the date after an early ultrasound, which is often the most accurate way to date a pregnancy. The American College of Obstetricians and Gynecologists explains how this is done in the source linked on this page. Use this tool to plan and to follow along week by week. For medical questions, and to confirm your dates, contact your healthcare provider. To count the days between two dates, try the Date Difference Calculator.