Due Date Calculator

Your due date (estimated delivery date, or EDD) is most commonly calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This method, known as Naegele's rule, assumes a 28-day cycle with ovulation on day 14. If you know your conception date, your due date is estimated as conception date plus 266 days (38 weeks).

A due date calculator gives an estimated delivery date, not a guaranteed one. Only about 4–5% of babies are born on their exact due date; most arrive within a window of two weeks before or after the calculated date. An early ultrasound, typically done between 8 and 13 weeks, is considered the most accurate method for confirming your due date.

Yes. If you know the approximate date of conception, you can calculate your due date by adding 266 days (38 weeks) to that date. Many due date calculators — including those for IVF patients — support conception-date or transfer-date input as an alternative to the LMP method.

Gestational age is the number of weeks and days your pregnancy has progressed, counted from the first day of your last menstrual period — not from conception. A full-term pregnancy is typically 40 weeks of gestational age. Knowing your gestational age helps your healthcare provider monitor fetal development and schedule appropriate prenatal tests.

For a 3-day IVF embryo transfer, add 263 days (37 weeks and 4 days) to your egg retrieval date, or simply subtract 3 days from a standard 40-week LMP calculation. For a 5-day blastocyst transfer, add 261 days (37 weeks and 2 days) from retrieval. Your fertility clinic will provide the exact transfer date to plug into the calculator.

Pregnancy is divided into three trimesters. The first trimester runs from week 1 through week 12, covering early development and the highest risk of miscarriage. The second trimester spans weeks 13 through 26, when most parents learn the baby's sex and the pregnancy becomes more visible. The third trimester covers weeks 27 through 40 (or beyond), ending at delivery.

Your due date is the estimated 40-week mark calculated from your LMP — it is a statistical midpoint, not a firm deadline. Your actual delivery date is when labor begins and the baby is born, which may naturally occur anywhere from 37 to 42 weeks of gestation. Births before 37 weeks are considered preterm, while those at or after 42 weeks may prompt medical intervention.