Pregnancy Due Date & Gestational Age Calculator
Calculate your estimated due date, track current pregnancy week and day, and explore fetal development milestones using Naegele’s rule.
First Day of Last Period
How is it calculated?
\text{Due Date} = \text{LMP} + 280 \text{ days} + (\text{Cycle Length} - 28)Uses Naegele’s Rule (LMP + 1 year - 3 months + 7 days), dynamically adjusted for individual menstrual cycle durations.
Worked Examples
LMP on January 1st with a standard 28-day cycle
Estimated Due Date (EDD) is October 8th of the same year (280 days total gestational duration).
The Essential Pregnancy Due Date & Gestational Milestone Guide
How Gestational Due Dates are Calculated: Naegele’s Rule
A full-term human pregnancy averages 40 weeks (280 days) from the first day of the last menstrual period (LMP). In 1812, German obstetrician Franz Naegele established the standard formula: take the first day of the LMP, add one year, subtract three months, and add seven days.
Our calculator accounts for individual menstrual cycle lengths. Because ovulation occurs roughly 14 days before the next period, women with shorter or longer cycles have their due dates automatically adjusted for ovulation offset.
Navigating the Three Trimesters of Pregnancy
The First Trimester (Weeks 1 to 13) encompasses conception, implantation, and rapid organogenesis, during which the embryo develops all major organ systems. Morning sickness and fatigue are most common here.
The Second Trimester (Weeks 14 to 27), often called the golden trimester, brings increased energy, visible baby growth, fetal movements (quickening), and the 20-week anatomy scan. The Third Trimester (Weeks 28 to 40) is focused on rapid fetal weight gain and preparation for labor.
Frequently Asked Questions
How accurate is an Estimated Due Date (EDD)?
What is the difference between gestational age and fetal age?
When is a pregnancy officially considered full term?
Results are estimates and should not be considered financial advice.