Calculate your estimated due date and current pregnancy week based on your last menstrual period (LMP) or conception date. Based on Naegele's Rule.
This calculator is a reference tool based on Naegele's Rule. The due date is an estimate of 280 days (40 weeks) from the last menstrual period. Actual delivery typically occurs within 2 weeks of the due date. For accurate pregnancy dating, please consult your healthcare provider for an ultrasound examination. This tool does not replace medical diagnosis.
"Last Period (LMP)" is the most common method, based on the first day of your last menstrual period. "Conception Date" is used when you know your ovulation or conception date. For IVF, use the embryo transfer date but follow your doctor's guidance.
Select or enter the relevant date. If you don't know the exact date, an ultrasound at your healthcare provider can help determine it.
Your due date, current pregnancy week, days remaining, and current trimester are displayed. The trimester timeline and developmental milestones are also shown. Green-highlighted milestones have already passed.
Naegele's Rule is a due date calculation method proposed in the 1830s by German obstetrician Franz Karl Naegele. Formula: Last Menstrual Period + 280 days (40 weeks) Or simply: Subtract 3 months from the LMP month and add 7 days This formula assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. If your cycle is irregular or not 28 days, the actual due date may differ. For conception-based calculation: Conception date + 266 days (38 weeks), since the actual gestation period after conception is approximately 38 weeks.
First Trimester (Weeks 1-12): - Implantation, placenta formation begins - Major organs and nervous system developing - Morning sickness, fatigue, breast changes - Highest risk of miscarriage - Folic acid intake especially important Second Trimester (Weeks 13-27): - Stable period, morning sickness decreases - Fetal movements begin (weeks 16-20) - Gender can be determined (weeks 16-20) - Detailed anatomy ultrasound (around week 20) - Stretch marks, skin changes possible Third Trimester (Weeks 28-40): - Rapid fetal growth and weight gain - Lung maturation progressing - Braxton Hicks contractions (practice contractions) - Pelvic pressure, swelling, back pain increase - Considered full term after week 37
Typical prenatal care schedule: Early Pregnancy (Weeks 8-12): - First prenatal visit and ultrasound - Blood type, anemia, hepatitis, STI screening - Cervical cancer screening Weeks 11-13: - First trimester screening (nuchal translucency) - NT ultrasound Weeks 15-20: - Second trimester screening (quad test) - Amniocentesis (if high risk) Weeks 20-24: - Detailed anatomy ultrasound Weeks 24-28: - Gestational diabetes screening (OGTT) - Anemia check After Week 28: - Biweekly checkups - Weekly after week 36 - GBS screening (weeks 35-37) - NST (non-stress test) as needed Schedule may vary based on maternal age, health, and risk factors.
Only about 5% of babies are born on their exact due date. Most deliveries occur within 2 weeks of the due date (38-42 weeks), which is considered normal. Before 37 weeks is preterm, and after 42 weeks is post-term. First pregnancies tend to go past the due date.
Irregular periods can make LMP-based calculations inaccurate. In such cases, an early ultrasound (CRL measurement) provides a more accurate due date. First trimester ultrasound (8-12 weeks) is generally most accurate.
If you don't know your exact conception date, use the LMP method. Ovulation typically occurs about 14 days before the next period, but this varies. The most accurate method is ultrasound measurement of fetal size by your healthcare provider.
Pregnancy weeks are counted from the LMP, which is about 2 weeks before conception actually occurs. So at '10 weeks pregnant,' the actual fetal age is about 8 weeks. Medically, gestational age (from LMP) is the standard measure.
Twin pregnancies typically deliver 2-3 weeks earlier than singleton pregnancies, usually around weeks 37-38. However, this calculator is designed for singleton pregnancies. For multiple pregnancies, consult your healthcare provider.
Yes, early ultrasound findings may adjust the due date. If the LMP-based and ultrasound-based dates differ by more than 7 days, the ultrasound date is typically used. Your healthcare provider will determine the final due date.