Free Pregnancy Due Date Calculator - EDD Calculator

Enter Your Last Menstrual Period

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Year

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Estimated Due Date

1st Trimester

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Weeks Pregnant

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Days Remaining

1st

Current Trimester

How Your Due Date Is Calculated

Your estimated due date (EDD) is calculated using Naegele's rule, one of the most widely used methods in obstetrics. The formula adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This method assumes a standard 28-day menstrual cycle with ovulation occurring around day 14. While it is a reliable estimate, only about 5% of babies arrive on their exact due date — most healthy pregnancies fall within a two-week window around the estimated date.

The reason the calculation starts from your LMP rather than the date of conception is that most women know when their last period began but the exact date of ovulation and fertilization can be difficult to pinpoint. In a typical 28-day cycle, conception usually occurs about two weeks after the LMP, which is why pregnancy is counted as 40 weeks from LMP even though the embryo has only been developing for about 38 weeks.

Understanding Your Trimesters

Pregnancy is divided into three trimesters, each lasting approximately 12 to 14 weeks. Each stage brings unique developmental milestones for your baby and physical changes for you.

First Trimester (Weeks 1-12): Your baby's major organs begin forming. You may experience fatigue, nausea, and mood swings. The risk of miscarriage is highest during this period, but drops significantly after week 12.
Second Trimester (Weeks 13-27): Often called the "golden trimester" as many early symptoms ease. Your baby grows rapidly, you may feel first movements (quickening), and the pregnancy becomes more visible. Use our Baby Feeding Calculator to start planning ahead.
Third Trimester (Weeks 28-40): Your baby gains weight rapidly and prepares for birth. You may experience more discomfort as your baby grows. Your healthcare provider will monitor you more frequently during this period.

Remember: Due Dates Are Estimates

While a due date provides a helpful target, it is important to remember that it is an estimate, not a deadline. Only about 4% of babies arrive on their predicted due date. Many factors influence when labor begins, including genetics, baby's position, and whether this is your first pregnancy. About 57% of first-time mothers go past their due date while subsequent pregnancies tend to be slightly shorter.

Your healthcare provider will monitor your pregnancy closely as you approach and pass your due date. Non-stress tests, ultrasounds, and amniotic fluid checks help ensure your baby remains healthy. Induction is generally recommended between 41 and 42 weeks to reduce the risk of complications. For your baby's early health tracking, consider our Baby Feeding Calculator and Conception Date Calculator.

Frequently Asked Questions

How accurate are due dates?

Only about 5% of babies are born on their exact due date. The due date is an estimate based on a 280-day pregnancy. Most babies arrive between 37 and 42 weeks, so the due date is really a target date rather than a deadline.

What if I don't know my last menstrual period?

If you are unsure of your last menstrual period, an early ultrasound can help determine your due date. Your healthcare provider will measure the baby's size to estimate gestational age, which is most accurate in the first trimester.

Can my due date change after an ultrasound?

Yes, an early ultrasound may adjust your due date by a few days to a week. Early ultrasounds (before 14 weeks) are the most accurate for dating a pregnancy. Your provider will typically use the earliest ultrasound measurement to set or confirm your due date.

How many weeks is a full-term pregnancy?

A full-term pregnancy is considered to be between 39 and 40 weeks gestation. Early term is 37-38 weeks, late term is 41 weeks, and post-term is 42 weeks and beyond.

What if I go past my due date?

Going past your due date is common — about 6% of pregnancies continue beyond 42 weeks. Your healthcare provider will monitor you closely. Induction is typically recommended between 41 and 42 weeks to reduce risks.

What trimester am I in?

Pregnancy is divided into three trimesters. The first trimester is weeks 1-12, the second is weeks 13-27, and the third is weeks 28-40. Each trimester brings different developmental milestones and physical changes.

Related Calculators

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Ovulation Calculator — Find your fertile window

Baby Feeding Calculator — Plan your baby's feeding schedule

BMI Calculator — Track your pregnancy weight

Calorie Deficit Calculator — Plan post-pregnancy weight management

Water Intake Calculator — Stay hydrated during pregnancy