Adjust the inputs below. Results update as you type.
Gestational age is counted from the first day of the last menstrual period (LMP), not conception—so 'two weeks pregnant' typically predates fertilization. First trimester: weeks 1–13. Second: 14–26. Third: 27–40. Anatomy ultrasound at 18–20 weeks screens for structural anomalies. GBS screening at 36 weeks. Full term is 39–40 weeks; early term 37–38 weeks.
Estimates due date as LMP + 280 days (Naegele-style rule). Your provider may use ultrasound dating instead.
Estimated due date
Thursday, October 8, 2026