Estimate an expected due date and gestational age based on the first day of the last menstrual period (LMP).
Use the first day of your last menstrual period to estimate due date.
Pregnancy due date calculators often use a simple estimate called Naegele’s rule. The calculation starts from the first day of the last menstrual period (LMP) and adds 280 days (40 weeks). This works because pregnancy length is typically measured from LMP rather than the conception date, which can be difficult to determine precisely.
The estimated gestational age is calculated by counting the days from LMP to today and converting that value into weeks and days. This number helps clinicians and patients track pregnancy milestones, schedule recommended prenatal visits, and interpret ultrasound findings.
Due dates are estimates, not guarantees. Menstrual cycle length, ovulation timing, and early ultrasound measurements can shift the expected date. For the most accurate dating and medical guidance, consult an obstetric clinician.
Disclaimer: This tool is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for diagnosis or treatment.This tool is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for diagnosis or treatment.