Due Date Calculator

Understanding Pregnancy Due Dates

A pregnancy due date, also known as the estimated date of delivery (EDD), is the predicted date when a pregnant woman is most likely to give birth. While only about 5% of babies are born exactly on their due date, most deliveries occur within two weeks before or after this date.

Our due date calculator uses established medical formulas to estimate your baby's arrival based on different calculation methods. Understanding your due date helps you track your pregnancy progress and prepare for your baby's birth.

How Due Dates Are Calculated

Last Menstrual Period (LMP) Method

This is the most common method used by healthcare providers. The due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period.

Conception Date Method

If you know the exact date of conception, the due date is calculated by adding 266 days (38 weeks) to that date.

Ultrasound Dating

Early ultrasound measurements (especially between 8-13 weeks) can provide a very accurate due date estimate based on fetal size and development.

Pregnancy Trimesters Explained

First Trimester (Weeks 1-13)

The first trimester is a period of rapid development. By the end of this trimester, all major organs have begun to form. Common experiences include morning sickness, fatigue, and breast tenderness.

Second Trimester (Weeks 14-26)

Many women find the second trimester more comfortable. Morning sickness typically subsides, and the baby's movements become noticeable. This is when most people have their anatomy scan ultrasound.

Third Trimester (Weeks 27-40+)

The baby gains most of its weight during this trimester. Common experiences include back pain, heartburn, and Braxton Hicks contractions. The baby typically moves into head-down position in preparation for birth.

Factors That Can Affect Your Due Date

Irregular Menstrual Cycles

If your menstrual cycle is longer or shorter than the average 28 days, your due date calculation may need adjustment. Our calculator accounts for different cycle lengths.

Ovulation Timing

Women who ovulate earlier or later in their cycle may have conception dates that don't align with the standard LMP calculation.

Multiple Pregnancies

Twins and other multiples often arrive earlier than singleton pregnancies, typically around 36-37 weeks rather than 40 weeks.

First vs. Subsequent Pregnancies

First babies are more likely to be late, while subsequent pregnancies often deliver closer to (or before) the due date.

Preparing for Your Baby's Arrival

First Trimester (Weeks 1-13)

Schedule your first prenatal appointment, start taking prenatal vitamins, and begin making lifestyle adjustments like avoiding alcohol and certain foods.

Second Trimester (Weeks 14-26)

Consider childbirth education classes, create a birth plan, and start planning your baby's nursery. This is also a good time to think about maternity leave.

Third Trimester (Weeks 27-40+)

Pack your hospital bag, install the car seat, finalize baby names, and prepare your home for the new arrival. Consider preparing freezer meals for the postpartum period.

When to Contact Your Healthcare Provider

While due dates are estimates, certain situations warrant contacting your healthcare provider:

1. No fetal movement - After previously feeling regular movement
2. Vaginal bleeding - Especially if it's heavy or accompanied by pain
3. Regular contractions - Before 37 weeks (could indicate preterm labor)
4. Your water breaks - Even if contractions haven't started
5. Severe headaches - Or visual changes (possible sign of preeclampsia)
6. Reaching 41 weeks - Without signs of labor (may require monitoring)

Remember that every pregnancy is unique. These guidelines provide general information, but your healthcare provider can offer personalized advice based on your specific situation.