Pregnancy Due Date Calculator

1. Select how you want to calculate: by last period, conception, or IVF transfer.
2. Enter the relevant date.
3. View your estimated due date and how far along you are.
4. Check key dates for each trimester transition.
5. Review development milestones week by week.
6. Copy the due date to share with family or healthcare providers.

What is a Pregnancy Due Date Calculator?

A pregnancy due date calculator estimates the date your baby is expected to be born based on either the first day of your last menstrual period (LMP), your known conception date, or your IVF embryo transfer date. The due date, also called the estimated date of delivery (EDD), gives expectant parents and healthcare providers a timeline for prenatal care, milestone tracking, and birth preparation. It is important to understand that a due date is an estimate, not a guarantee. Only about 5% of babies are born on their exact due date. Most births occur within a two-week window on either side, between weeks 38 and 42 of pregnancy.

How Due Date Calculations Work

The standard method for calculating a due date is Naegele's Rule, developed by German obstetrician Franz Naegele in the early 1800s. The formula adds 280 days (40 weeks) to the first day of your last menstrual period. This is based on the assumption that ovulation and conception occur approximately 14 days after the start of menstruation in a standard 28-day cycle. If your cycle is longer or shorter than 28 days, the estimate may shift by a few days.

For women who know their exact conception date (through ovulation tracking, for example), the calculator adds 266 days from conception. For IVF pregnancies with a 5-day embryo transfer, the calculation adds 261 days from the transfer date (266 minus 5 days of embryo development). The IVF method tends to be the most accurate because the date of fertilization is known precisely.

Common Use Cases

• Estimating your due date as soon as you learn you are pregnant
• Planning prenatal appointments and scheduling ultrasounds
• Tracking which trimester you are in and what developmental milestones to expect
• Coordinating maternity or paternity leave with your employer
• Preparing your home, nursery, and hospital bag on a timeline
• Sharing a timeline with family members and support networks

Understanding the Three Trimesters

Pregnancy is divided into three trimesters, each lasting approximately 13 to 14 weeks. The first trimester (weeks 1 through 12) is the most critical period for fetal development. During this time, all major organs begin to form, the neural tube develops into the brain and spinal cord, and the heart begins beating. This is also when morning sickness and fatigue are most common for the mother.

The second trimester (weeks 13 through 26) is often called the "golden period" because many early pregnancy symptoms subside. The baby grows rapidly, and most parents begin to feel fetal movement (known as "quickening") between weeks 18 and 22. Anatomy scans are typically performed around week 20 to check for structural abnormalities.

The third trimester (weeks 27 through 40) focuses on brain development, weight gain, and preparation for birth. The baby gains roughly half of its birth weight during this final stage. The lungs mature, the baby settles into a head-down position in most cases, and the body prepares for labor. Regular prenatal visits become more frequent during this period, typically every two weeks and then weekly as the due date approaches.

Remember that a "normal" full-term pregnancy can last anywhere from 37 to 42 weeks. Your healthcare provider may adjust your due date based on early ultrasound measurements, especially if the LMP-based estimate differs from the ultrasound by more than a week. Always consult your doctor or midwife for personalized prenatal care and guidance.

Related Health Tools

Support your overall health during pregnancy by tracking your nutrition with the Calorie Calculator and Macro Calculator. You can also check your weight classification with the BMI Calculator or explore your target weight with the Ideal Weight Calculator.