Pregnancy Due Date Calculator

LMP stands for "Last Menstrual Period," and it is the standard starting point used by healthcare providers to date a pregnancy and estimate a due date. Since most women do not know the exact moment of conception, doctors count from the first day of the last period when the egg-thickening process began. This method assumes a standard 28-day cycle with ovulation occurring on day 14, making the total pregnancy length about 40 weeks. Using the LMP is the most consistent way to track your pregnancy milestones across different medical practices.

A full-term pregnancy is professionally defined as lasting approximately 40 weeks, or 280 days, from the first day of your last menstrual period. This duration is divided into three trimesters, each involving distinct stages of fetal development and maternal changes. While 40 weeks is the target, any birth between 37 and 42 weeks is considered within the normal full-term range. Our calculator tracks your progress through these weeks to help you prepare for each development stage as your due date approaches.

The first trimester begins on the first day of your LMP and lasts until the end of week 13; this is a critical period for organ development. The second trimester starts at week 14 and continues through week 27, often referred to as the "golden period" when many women feel their best. Finally, the third trimester begins at week 28 and lasts until birth, as the baby focuses on rapid growth and weight gain. Tracking these trimesters helps you organize your prenatal care and prepare your home for the baby's arrival.

No, the estimated due date is just an estimate, and only about 5% of babies are actually born on their exactly calculated date. Most babies arrive within a two-week window before or after the EDD, which is perfectly normal and healthy for the mother and child. Your due date may also be adjusted later by your doctor based on ultrasound measurements, which are more accurate for dating in the first trimester. Think of your EDD as a general goalpost rather than a definitive appointment for the baby's arrival.

For pregnancies achieved through In-Vitro Fertilization (IVF), the due date is calculated based on the specific embryo transfer date and the age of the embryo. If a 5-day blastocyst was transferred, the calculation counts back 14 days and then 5 days to find the "equivalent LMP" date. This method is much more precise than LMP dating because the exact moment the embryo was introduced to the womb is known and recorded. Our calculator includes an IVF option to ensure you get the most accurate possible timeline for your fertility journey.