Pregnancy Due Date Calculator
Calculate your estimated due date and current pregnancy week from your LMP, conception date, or ultrasound.
Estimated Due Date
Wednesday, June 30, 2027
Pregnancy Due Date Calculator
Calculate your Estimated Due Date (EDD), current trimester, and fetal development milestones based on the First Day of your Last Menstrual Period (LMP) or conception date.
The moment a pregnancy is confirmed, the immediate question is: "When is the baby due?" While nature ultimately decides the exact arrival time, establishing an Estimated Due Date (EDD) is the foundational metric of all prenatal care. It dictates when critical ultrasound screenings occur, when specific nutritional supplements are required, and how doctors monitor fetal growth percentiles. The Pregnancy Due Date Calculator utilizes standard obstetric mathematics to instantly project the timeline of your pregnancy, providing crucial milestones for the next nine months.
The Science of Naegele's Rule
The standard global medical calculation is known as Naegele's Rule. The formula adds 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP).
A simpler way to calculate it manually is to take the first day of your LMP, add 7 days, and subtract 3 months. Our calculator automates this math flawlessly, instantly navigating across calendar years and leap years to provide the exact target date. It also automatically adjusts the math if you input a menstrual cycle length that is longer or shorter than the standard 28 days.
Gestational Age vs. Fetal Age
A concept that severely confuses new parents is the difference between Gestational Age and Fetal Age. According to the medical LMP calculation, you are considered "two weeks pregnant" before conception even occurs.
Because the exact day of ovulation and fertilization is difficult to pinpoint, doctors start the clock on the first day of the last period. Therefore, a full-term pregnancy is technically 40 weeks of Gestational Age, but the baby (Fetal Age) is actually only about 38 weeks old. The calculator handles these medical definitions so you can communicate accurately with your OB-GYN.
How to Use the Calculator
The most accurate method is to select the "Last Menstrual Period (LMP)" tab. Input the exact date the bleeding started for your last period. Next, input your average cycle length (e.g., 28 days, 32 days).
If you underwent IVF (In Vitro Fertilization) or know the exact date of conception via tracking, select those respective tabs for a slightly altered, highly specific calculation. The tool will output your EDD, your current week/trimester, and a timeline of critical developmental milestones. To ensure you are maintaining a healthy diet during these trimesters, consult our Macronutrient Calculator.
When Ultrasound Overrides the Math
It is vital to understand that this calculator provides an estimate based on calendar math. Only about 4% to 5% of babies are actually born on their exact Estimated Due Date.
Furthermore, if you have irregular menstrual cycles, the LMP math can be highly inaccurate. The definitive, ultimate source of truth for your due date is the First Trimester Ultrasound (the "dating scan"). The doctor will measure the physical length of the fetus (Crown-Rump Length). If the ultrasound date differs from the LMP math by more than a week, the doctor will officially change your due date based on the physical measurement.
Expert Insights & FAQs
Quick answers to common questions about this utility.
What does it mean if a baby is born 'Preterm'?
A standard pregnancy is 40 weeks. A baby is considered 'Full Term' if born anywhere between 39 weeks and 40 weeks 6 days. 'Preterm' refers to any delivery that occurs before 37 complete weeks of gestation, which often requires neonatal intensive care.
Can I use this calculator if I have PCOS and irregular periods?
If your cycles vary wildly (e.g., 35 days one month, 60 days the next), the LMP calculation will be highly inaccurate because the date of ovulation is completely unknown. In this case, you must wait for the dating ultrasound to establish an accurate due date.
Why do doctors let pregnancies go past the due date?
The due date is just the middle of a statistical bell curve. It is perfectly normal and safe to remain pregnant up to 41 weeks or even 42 weeks (Post-Term). However, doctors carefully monitor the placenta function during this time, and will usually recommend medical induction before 42 weeks.