Pregnancy Due Date Calculator
Calculate your Estimated Due Date (EDD), current trimester, and track important pregnancy milestones.
Understanding Your Estimated Due Date (EDD)
What is an EDD?
Your Estimated Due Date (EDD), or Estimated Date of Delivery, is the primary cornerstone of your prenatal care. It provides a timeline for healthcare providers to schedule critical developmental scans, blood tests, and prepare for birth.
Historically, predicting the specific day of a baby's arrival is complex. Even today, the EDD serves as the median point of an acceptable birth window. Any delivery between 37 weeks and 42 weeks is considered normal and healthy by modern obstetrics.
The Mathematics of Pregnancy
This clinical formula, developed by German obstetrician Franz Karl Naegele, has been the global standard for dating pregnancies for over two centuries. It assumes a standard 28-day menstrual cycle.
Days = 280 + (Cycle Length - 28)Different Calculation Methods
Last Menstrual Period (LMP)
The most common method used by doctors. Since exact conception dates are rarely known, the first day of an individual's last period is used as a verified starting point. Pregnancy officially begins counting two weeks before conception actually happens.
Conception Date
Used when basal body temperature or ovulation tracking strips confirm the exact day of ovulation and conception. The calculator simply adds 266 days (38 weeks) directly to this date.
IVF Transfer
Due to the precise nature of medical intervention, IVF dating is highly accurate. Calculating EDD involves adding specific days to the transfer date depending on whether a 3-day or 5-day embryo (blastocyst) was used.
The Three Trimesters
A standard 40-week pregnancy is broken into three distinct stages of fetal development and maternal changes.
- T1First Trimester (Weeks 1-12)
The fundamental architecture of the baby is built. By the end of twelve weeks, all basic organ systems exist. Hormonal shifts often trigger morning sickness and fatigue.
- T2Second Trimester (Weeks 13-26)
Usually deemed the most comfortable phase. Energy returns, and anatomical ultrasound anomalies are checked around week 20. Fetal movement (quickening) is typically felt.
- T3Third Trimester (Weeks 27-40+)
Rapid final growth and weight gain for the baby. Lung and brain maturity are finalized. The mother begins preparing physiologically and mechanically for labor.
When Are Babies Actually Born?
Only a fraction of pregnancies culminate precisely on the EDD. Modern studies suggest shifting perspective from a "Due Date" to a "Due Month".
Frequently Asked Questions (Pregnancy Dates)
Strict Medical Disclaimer
The dates provided by this calculator are mathematical estimates based on global averages and standard obstetrical formulas (Naegele's rule).
This tool is not intended to provide a medical diagnosis or substitute early pregnancy clinical dating. An ultrasound performed by a healthcare professional between weeks 8 and 12 is the only definitive way to measure fetal size (Crown-Rump Length) and establish a clinically actionable dating timeline.