Due Date Calculator
Estimate pregnancy due date from last menstrual period.
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Frequently asked questions
It is an estimate, not a medical prediction. Naegele's rule assumes a 28-day cycle and ovulation on day 14, and only a small percentage of pregnancies actually deliver on the exact due date. Talk to a clinician for a personalized estimate based on ultrasound dating.
The calculator adds (cycle length − 28) days on top of the standard 280-day window. A 35-day cycle shifts the due date about a week later; a 25-day cycle shifts it about three days earlier.
The first trimester starts on the LMP date. The second trimester starts at week 14 (91 days after LMP) and the third trimester starts at week 28 (189 days after LMP). These are the conventional clinical week boundaries.
Last updated 2026-06-03.