Pregnancy Due Date Calculator
Estimate your baby's arrival date using multiple calculation methods
Medical Disclaimer
This calculator provides an estimate for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider for prenatal care and accurate medical information. Every pregnancy is unique.
Calculation Methods
Choose the method that matches the information you have available. Click on any method below to use it directly.
Last Menstrual Period (LMP)
Most common method. Uses the first day of your last period and your average cycle length. Best for: Regular menstrual cycles.
Conception Date
Uses the exact date of conception if known. Adds 266 days (38 weeks) from conception. Best for: When conception date is certain.
IVF Transfer Date
For IVF pregnancies. Uses embryo transfer date and embryo age (3-day or 5-day blastocyst). Best for: IVF/fertility treatment pregnancies.
Ultrasound Measurement
Uses gestational age from an ultrasound. Most accurate when done in the first trimester. Best for: Dating ultrasound available.
How the Due Date is Calculated
The estimated due date (EDD) is calculated using Naegele's Rule, the standard method used by healthcare providers. Pregnancy is measured from the first day of your last menstrual period (LMP), even though conception occurs about two weeks later.
Naegele's Rule
Add 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14.
Cycle Length Adjustment
If your cycle is longer or shorter than 28 days, the due date is adjusted accordingly. A 35-day cycle would add 7 days to the due date.
Important Pregnancy Information
The following information is based on guidelines from ACOG (American College of Obstetricians and Gynecologists), WHO (World Health Organization), and other trusted medical sources.
Due Date Accuracy
Only about 4-5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after. (Source: ACOG)
Full Term Definition
Per ACOG: Early term (37w0d-38w6d), Full term (39w0d-40w6d), Late term (41w0d-41w6d), Post-term (42w0d+).
Ultrasound Dating
First-trimester ultrasounds (before 14 weeks) are most accurate for dating, typically within 5-7 days of the actual gestational age.
Prenatal Care
Regular prenatal visits are essential. WHO recommends at least 8 contacts with healthcare providers during pregnancy.
Trimester Guide
Pregnancy is divided into three trimesters, each with distinct developmental milestones.
First Trimester (Weeks 1-12)
- • All major organs begin to form
- • Heart begins beating around week 6
- • Brain and spinal cord develop
- • By week 12, baby is about 2 inches long
- • Risk of miscarriage decreases significantly after week 12
Second Trimester (Weeks 13-26)
- • Baby can hear sounds
- • Movements become noticeable (quickening)
- • Sex may be visible on ultrasound around week 18-20
- • Anatomy scan typically performed around week 18-22
- • By week 24, baby has reached viability milestone
Third Trimester (Weeks 27-40)
- • Lungs continue maturing
- • Baby gains weight rapidly
- • Brain develops rapidly
- • Baby typically moves into head-down position
- • At full term (39+ weeks), baby is typically 19-21 inches long
Frequently Asked Questions
How is the due date calculated?▼
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What if my cycle is irregular?▼
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Information Sources
- • American College of Obstetricians and Gynecologists (ACOG)
- • World Health Organization (WHO) - Recommendations on Antenatal Care
- • National Institutes of Health (NIH)