Calculating Your Due Date: The Science of Gestational Timelines
The day you find out you are pregnant is filled with excitement and questions — and the first question is inevitably: when will my baby arrive?
Our pregnancy due date calculator is built to analyze your dates using medical benchmarks, helping you understand your current week of pregnancy, trimester milestones, and estimated due date instantly.
Naegele's Rule: The Standard LMP Calculation
Obstetricians typically determine due dates using Naegele's rule, which assumes a standard gestational cycle of 280 days (40 weeks) starting from the first day of your Last Menstrual Period (LMP). This rule assumes a perfect 28-day menstrual cycle with ovulation occurring on day 14.
However, many women have cycle lengths ranging from 21 to 45 days. Our tool allows you to adjust the average cycle length, shifting the due date proportionally to account for later or earlier ovulation.
Trimester Timelines: Dividing Your Pregnancy
Pregnancy is divided into three distinct phases called trimesters, marked by major developmental stages:
- First Trimester (Weeks 1 to 12): The critical period of organ development (organogenesis). By week 12, all major organs are formed.
- Second Trimester (Weeks 13 to 27): The period of rapid growth. This is usually when expecting mothers begin feeling movement (quickening) and discover the baby's gender.
- Third Trimester (Weeks 28 to 40): The final stretch where the lungs fully mature, the brain expands rapidly, and the baby gains weight to prepare for birth.
Weekly Fruit Size Guide: Visualizing Your Baby's Growth
Visual comparisons are a fun and memorable way to track fetal development. Our guide maps your pregnancy to familiar fruits, from a poppy seed at week 4 to a full-size pumpkin at week 40, helping you visualize the amazing changes occurring week-by-week.