Due Date Calculator

Enter the first day of your last period to find out when your baby is due.

This is an estimate. If your provider has set a due date after an early ultrasound, that's the one to follow — ultrasound dating is more accurate than LMP, especially for irregular cycles.

What to track during pregnancy (besides the weeks)

The due-date number above is the starting line. What actually shapes how your pregnancy unfolds — and what your provider wants to see at every visit — is the data you collect between appointments.

Symptoms by trimester

In the first trimester, log nausea (time of day + severity), fatigue, food aversions, and any spotting or cramping. In the second, watch for the first kicks (typically weeks 18-22), round-ligament pain, and skin changes. In the third, baby movement counts (after week 28), Braxton Hicks contractions, swelling, and headaches are what your OB or midwife will ask about — and sudden changes are what they actually want to hear.

Weight, blood pressure, and mood

Weekly weight is more useful than monthly: the curve matters more than the number (typical total: 25-35 lbs for an average BMI). Blood pressure can flag preeclampsia early if your provider has asked you to check at home. Mood is the most-skipped tracker — prenatal depression affects roughly 1 in 7 women, and a written log catches the slow drift much earlier than a memory check at your 30-week appointment.

What ongoing tracking actually unlocks

A calculator answers "when." A tracking app answers "what's normal for me?" — which is the question your provider is trying to answer at every visit. For a trimester-by-trimester checklist of what to log and what to bring to each prenatal appointment, see our pregnancy tracking guide. If your pregnancy is ongoing, the pregnancy wellness tips guide covers what to focus on week by week.

Up next: Once your pregnancy is underway, the pregnancy week calculator tells you exactly what's happening with baby this week. Trying again later? The ovulation calculator finds your fertile window. Already postpartum? The period calculator helps you make sense of cycles that haven't yet settled.

Due dates shift. Your tracker should keep up.

Unsure of your LMP, or your cycles aren't a textbook 28 days? Gaia refines your due date as you log symptoms, ultrasound dates, and your real cycle history — so what your doctor sees and what your app shows actually agree.

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Common 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.

Educational content, not medical advice. This calculator uses Naegele's Rule to give you an estimated due date, not a diagnosis or treatment recommendation. For pregnancy care, fertility planning, or any symptoms that concern you, please consult your OB-GYN, midwife, or other healthcare provider. Go Go Gaia is a tracking tool, not a substitute for professional medical care. Contact your provider right away for heavy bleeding, severe pain, or reduced fetal movement.