Due Date Calculator
Calculate your estimated due date (EDD) from your last menstrual period or IVF transfer date. Includes trimester timeline and gestational age.
Frequently Asked Questions
How is my due date calculated?
We use Naegele's Rule, the standard method recommended by the American College of Obstetricians and Gynecologists (ACOG). Your estimated due date (EDD) is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP), then adjusting for your cycle length if it differs from the standard 28 days.
What is Naegele's Rule?
Naegele's Rule was established in the 19th century by German obstetrician Franz Karl Naegele. It calculates EDD as: LMP + 1 year − 3 months + 7 days, which is equivalent to LMP + 280 days. For cycles longer or shorter than 28 days, the EDD is adjusted accordingly.
How does the IVF calculator work?
For IVF pregnancies, the due date is calculated from the embryo transfer date. A Day 5 embryo transfer means the embryo is already 5 days old at transfer, so we subtract 5 from 266 (the average days from fertilization to delivery). A Day 3 transfer subtracts 3 instead. This gives an EDD equivalent to a natural conception.
How accurate is the due date calculator?
Only about 4% of babies are born on their exact due date. The EDD is a best estimate — most births occur within 2 weeks before or after. Your healthcare provider may adjust your due date based on ultrasound measurements, which can be more accurate, especially in the first trimester.
What if my cycle is irregular?
The cycle-length slider lets you enter your average cycle length (20–45 days). If your cycles are very irregular, speak with your OB or midwife. They may use first-trimester ultrasound dating, which tends to be more accurate than LMP-based methods for women with irregular cycles.
Clinical Source
Due date calculations on this page are based on methods described by the American College of Obstetricians and Gynecologists (ACOG) in Committee Opinion No. 700: Methods for Estimating the Due Date (May 2017). ACOG recommends using the LMP and ultrasound together for the most accurate dating. This tool is for informational purposes only and does not replace medical advice.