Pregnancy Due Date Calculator

Already Know How Many Weeks Pregnant You Are?

If a scan or your provider has told you how far along you are, enter it here to see your due date.

How it works: a pregnancy is counted as 40 weeks (280 days) from the first day of the last period. If you are 6 weeks pregnant today, there are 34 weeks left, so your due date is 34 weeks (238 days) from today. At 10 weeks, it is 30 weeks from today.

How Is Your Due Date Calculated?

Your estimated due date (EDD) is calculated using Naegele's Rule, a standard method used by healthcare providers worldwide:

• From Last Period (LMP): Add 280 days (40 weeks) to the first day of your last menstrual period
• From Conception: Add 266 days (38 weeks) to your conception date

The standard calculation assumes a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, this calculator moves the date by the difference. For example, with a 32-day cycle the due date is 4 days later.

Example: if your last period started on March 1, 2026 and your cycle is 28 days, your estimated due date is December 6, 2026 (March 1 + 280 days).

IVF pregnancies: the date is counted from the embryo transfer instead: transfer date + 261 days for a day-5 (blastocyst) transfer, or + 263 days for a day-3 transfer. Your fertility clinic will confirm the exact date.

What to do after using a due date calculator

A due date result is most useful when you treat it as a planning estimate rather than a promise. After using the calculator, use the date to:

• book or confirm your first prenatal appointment
• estimate when key screenings and the anatomy scan may happen
• track your current pregnancy week more easily
• prepare questions for your provider if your cycle is irregular or conception timing is unclear

If your main goal is fertility timing before pregnancy, go next to the ovulation calculator. If your goal is day-to-day pregnancy support, pair this page with the water intake calculator to stay steadier with hydration.

Understanding the Trimesters

First Trimester (Weeks 1-13): Your baby's major organs and systems begin to form. This is when many women experience morning sickness. It's important to start prenatal vitamins with folic acid.

Second Trimester (Weeks 14-27): Often called the "honeymoon period" as morning sickness typically subsides. You'll likely feel your baby's first movements (quickening) around weeks 18-20. The anatomy scan is usually done during this time.

Third Trimester (Weeks 28-40): Your baby gains weight rapidly and prepares for birth. You may experience Braxton Hicks contractions. Regular check-ups become more frequent.

Important Pregnancy Milestones

• Week 8: First prenatal appointment typically scheduled
• Week 10-12: First trimester screening available
• Week 12: Risk of miscarriage significantly decreases
• Week 18-20: Anatomy scan (mid-pregnancy ultrasound)
• Week 24: Viability milestone - baby has a chance of survival if born early
• Weeks 24–28: Glucose screening test for gestational diabetes
• Weeks 37–38: Early term
• Weeks 39–40: Full term, the safest time for most babies to be born
• Week 41: Late term; your provider will talk with you about monitoring or induction

How Accurate Is This Calculator?

While due date calculators use medically accepted formulas, only about 5% of babies are born on their exact due date. Most babies arrive within a two-week window before or after the estimated date. Your healthcare provider may adjust your due date based on:

• First-trimester ultrasound measurements (most accurate)
• Second-trimester ultrasound
• Irregular menstrual cycles
• IVF or assisted reproduction dates

Frequently Asked Questions

How is my due date calculated?

Your due date is calculated using Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If you know your conception date, add 266 days (38 weeks). The calculation assumes a 28-day cycle with ovulation on day 14.

How accurate is the due date calculator?

Due date calculators provide an estimate. Only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after. Your healthcare provider may adjust your due date based on ultrasound measurements, especially in the first trimester.

What are the three trimesters of pregnancy?

First Trimester (Weeks 1-13): Baby's organs begin forming. Second Trimester (Weeks 14-27): Baby grows rapidly, you may feel movements. Third Trimester (Weeks 28-40): Baby gains weight and prepares for birth.

When should I see a doctor after a positive pregnancy test?

Schedule your first prenatal appointment around 8 weeks after your last period. Contact your doctor sooner if you experience severe pain, heavy bleeding, or have a history of complications. Early prenatal care is important for a healthy pregnancy.

Related Calculators

• Ovulation Calculator - Find your fertile window
• Baby Growth Percentile Calculator - Track your baby's growth after birth
• BMI Calculator - Check your body mass index
• Water Intake Calculator - Stay hydrated during pregnancy