Pregnancy Calculator

About the Pregnancy Calculator

Knowing your pregnancy due date and current week is one of the most important pieces of information throughout pregnancy. Our pregnancy calculator determines your estimated due date (EDD) from your last menstrual period or conception date, tells you your current pregnancy week and trimester, and provides a week-by-week timeline of key milestones. Accurate gestational age dating is essential for prenatal care scheduling and monitoring fetal development.

How It Works

The estimated due date is calculated using Naegele's rule: EDD = LMP + 280 days (40 weeks). Gestational age in weeks = (Current Date − LMP) ÷ 7. Trimesters: First (weeks 1-12), Second (weeks 13-26), Third (weeks 27-40). Only 5% of babies are born on their exact due date — most deliveries occur within ±2 weeks of the EDD. If you know your conception date, EDD = conception date + 266 days (38 weeks).

Tips & Best Practices

• ✓Early ultrasound (8-12 weeks) is more accurate for dating than LMP calculation alone.
• ✓Key milestones: heartbeat detectable (6 weeks), gender possible (16-20 weeks), viability threshold (24 weeks).
• ✓First prenatal appointment recommended at 8-10 weeks; anatomy scan at 18-20 weeks.
• ✓The third trimester begins at week 27 (28 weeks is another common definition).
• ✓Group B Strep (GBS) testing occurs at 35-37 weeks in the USA.

Who Uses This Calculator

Expectant mothers tracking their pregnancy progress, healthcare providers scheduling prenatal appointments, birth photographers and doulas planning their schedules, and family members helping a pregnant loved one monitor milestones all use due date calculators.