Pregnancy Due Date Calculator
Calculate your estimated due date based on your last menstrual period (LMP) using Naegele's rule. Get trimester start dates, your current week of pregnancy, and days until your due date.
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Frequently Asked Questions
How is a due date calculated?
Using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). Or subtract 3 months and add 7 days to the LMP date. Both methods assume a 28-day cycle.
How accurate is the due date?
Only about 5% of babies are born on their exact due date. Most arrive within 2 weeks before or after. The due date is a guideline — the normal delivery window is 37 to 42 weeks of pregnancy.
What is gestational age vs fetal age?
Gestational age counts from the first day of the last menstrual period (LMP), which is the clinical standard. Fetal age (conception age) counts from fertilization — typically about 2 weeks less than gestational age.