How the Due Date Is Estimated

This conception calculator estimates your due date by adding 266 days (38 weeks) to the conception date — the standard gestational length measured from fertilization. Clinicians usually quote the LMP-based date (280 days from the first day of the last period), which is the same due date counted from two weeks earlier.

What to Expect

Only about 4% of babies are born exactly on their due date. A full-term pregnancy spans 39–40 weeks (days 266–280); early term is 37–38 weeks and late term is 41 weeks. Your healthcare provider will confirm dating with an early ultrasound, which is the most accurate method.

Disclaimer

This tool provides an estimate for informational purposes only and is not medical advice. Always consult a doctor or midwife for clinical pregnancy dating, prenatal care, and any concerns about your pregnancy.