🤰 Due Date Calculator

The most common method uses Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle isn't 28 days, the calculation adjusts accordingly. Only about 5% of babies arrive on their exact due date — most are born within 2 weeks before or after.

The estimated due date (EDD) is an approximation. Only about 4-5% of babies are born on their exact due date. Most babies arrive between 38-42 weeks. A first-trimester ultrasound provides the most accurate dating, typically within ±5-7 days.

You can use the Conception Date method if you know when you conceived, or the Ultrasound method where your doctor measures the baby's size. IVF patients can use their transfer date. Your healthcare provider can also estimate dates through a physical exam.

Gestational age is counted from the first day of your last period (about 2 weeks before conception). Fetal age (also called embryonic age) is counted from the actual date of conception. So fetal age is about 2 weeks less than gestational age.

Yes! If an ultrasound shows the baby measuring significantly different from the LMP-based date, your doctor may adjust your due date. Early ultrasounds (before 14 weeks) are the most accurate for dating.

First Trimester (Weeks 1-12): Organs form, heartbeat starts. Second Trimester (Weeks 13-26): Baby moves, gender visible. Third Trimester (Weeks 27-40): Rapid growth, lungs mature, preparing for birth.