Pregnancy Due Date Calculator

How Your Due Date is Calculated

The standard pregnancy lasts approximately 40 weeks (280 days) from the first day of your last menstrual period (LMP). Our calculator uses Naegele's Rule but improves upon it by adjusting for your specific cycle length. If your cycle is longer or shorter than the average 28 days, your ovulation date shifts, and our engine accounts for that variation to give you the most accurate prediction possible.

Understanding the Trimesters

Pregnancy is traditionally divided into three stages, each with its own developmental milestones:

• First Trimester (Weeks 1-12): A period of rapid development where all major organs begin to form. This is often when morning sickness is most prevalent.
• Second Trimester (Weeks 13-26): Often called the "honeymoon phase." Energy levels usually increase, and you will likely feel the baby's first movements.
• Third Trimester (Weeks 27-40): The final stretch where the baby grows significantly in size and weight, preparing for birth.

What Does "Full Term" Mean?

While 40 weeks is the "target," a baby is considered full term at 39 weeks. Being born between 39 weeks and 40 weeks and 6 days is ideal for healthy brain and lung development. Our tracker marks your 37-week milestone as "Early Term," which is the start of the window where delivery is considered safe.

Is the Due Date Guaranteed?

It is important to remember that a due date is an estimate. Only about 4-5% of babies are born exactly on their due date. Most babies arrive within a two-week window before or after the predicted date. Factors such as ultrasound measurements and maternal health may lead your doctor to adjust this date later in your pregnancy.