Pregnancy Calculator
Calculate your estimated due date, fetal age, and key pregnancy milestones.
Pregnancy Due Date & Milestone Calculator
Finding out you are expecting a baby is a thrilling moment, immediately followed by the most common question: "When is the baby due?" Our highly accurate Pregnancy Calculator helps you estimate your delivery date, track the current age of the fetus, and anticipate important trimester milestones.
How is the Due Date Calculated?
Most pregnancies last approximately 40 weeks (or 280 days), but the calculation isn't as simple as adding 9 months to the day of conception. In fact, standard medical practice calculates the due date based on the First Day of your Last Menstrual Period (LMP), not the conception date.
This method, known as Naegele's rule, works on the assumption of a standard 28-day menstrual cycle where ovulation occurs on day 14. The formula used is:
Pregnancy Trimesters Timeline
A full-term pregnancy is divided into three distinct phases, or trimesters. Understanding these milestones helps you prepare for the physical changes and medical checkups required.
- First Trimester (Weeks 1 through 12): A period of rapid cellular development. Major organs and the nervous system begin to form. This is also when early pregnancy symptoms (like morning sickness and fatigue) are most prominent.
- Second Trimester (Weeks 13 through 26): Often called the "honeymoon phase" of pregnancy. Nausea usually subsides, energy returns, and the mother begins to feel the baby move (quickening). The baby's sex can usually be determined via ultrasound mid-trimester.
- Third Trimester (Weeks 27 through 40+): The baby gains significant weight and lungs mature in preparation for birth. The mother may experience physical discomfort as the baby grows larger and presses against internal organs.
Important Limitations to Remember
An Estimated Due Date (EDD) is exactly that—an estimate. Only about 4% to 5% of babies are actually born precisely on their due date. Most women deliver within two weeks before or after the estimated date.
Furthermore, this calculator assumes a standard 28-day cycle. If you have irregular cycles, shorter cycles, or longer cycles, an early dating ultrasound performed by your obstetrician will provide the most accurate determination of gestational age.
Frequently Asked Questions
1. What if I don't remember my last menstrual period?
If you cannot remember the date of your LMP or your periods are highly irregular, your doctor will rely on a first-trimester ultrasound to measure the length of the fetus (crown-rump length) to establish a highly accurate due date.
2. Is it safe to use this calculator for IVF?
For In Vitro Fertilization (IVF), the due date calculation is based specifically on the date of embryo transfer and the age of the embryo (e.g., 3-day vs. 5-day transfer), not the last menstrual period. Specialized IVF calculators should be used.