👶 Due Date Calculator

The most common method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle. If your cycle is longer or shorter, the calculator adjusts accordingly.

Only about 5% of babies are born exactly on their due date. Most births occur within 2 weeks before or after the estimated due date. Your healthcare provider may adjust your due date based on ultrasound measurements.

The first trimester spans weeks 1–12, the second trimester weeks 13–27, and the third trimester begins at week 28 and continues until birth. Each trimester involves distinct developmental milestones for the baby.