Due Date Calculator
Enter the first day of your last period to find out when your baby is due.
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Download Go Go GaiaCommon Questions About Due Dates
Most due dates are calculated using Naegele's Rule: take the first day of your last menstrual period (LMP) and add 280 days (40 weeks). This assumes a 28-day cycle with ovulation on day 14. Your doctor may adjust your due date after an early ultrasound, which can be more accurate — especially if your cycles are irregular.
Only about 5% of babies arrive on their exact due date. Most are born within a two-week window on either side. Due date calculators based on your last period are a solid estimate, but first-trimester ultrasounds (between 8-12 weeks) tend to be the most accurate way to date a pregnancy. Think of your due date as a target range, not a deadline.
If you're not sure when your last period started, your doctor can estimate your due date with an early ultrasound. The earlier it's done, the more accurate it is — ideally between 8 and 12 weeks. This is one reason tracking your periods (even casually) is so helpful when you're trying to conceive or think you might be pregnant.
Yes, and it's pretty common. Your doctor might adjust your due date after an early ultrasound if baby's measurements suggest a different gestational age. This usually happens at your first prenatal appointment. Once a due date is set based on ultrasound, it typically stays — but every pregnancy is different.
Pregnancy is divided into three trimesters. The first trimester runs from weeks 1-12 (this is when nausea, fatigue, and sore breasts are most common). The second trimester is weeks 13-26 — often called the "honeymoon phase" because many symptoms ease up and you start feeling baby move. The third trimester is weeks 27-40, when baby is growing fast and you're getting ready for delivery.
Call your doctor or midwife as soon as you get a positive pregnancy test. Most providers schedule the first prenatal visit between 8-10 weeks. In the meantime, start taking a prenatal vitamin with folic acid if you aren't already, and avoid alcohol, smoking, and high-mercury fish. Early care gives you and your baby the best start.