Calculate your current pregnancy week, trimester, and estimated due date from your last menstrual period (LMP). Uses Naegele's rule.
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Due Date Formula (Naegele's Rule)
Due Date = LMP + 280 days (40 weeks) Adjusted for cycle length ≠ 28 days
This is a sensitive health topic. Please consult your doctor and gynaecologist for medical confirmation of pregnancy stage and due date through ultrasound scan.
Frequently Asked Questions
The LMP-based due date is an estimate with an accuracy window of about 2 weeks. Only 5% of babies are born exactly on the calculated due date. An ultrasound scan in the first trimester gives a more accurate estimate.
The first trimester is weeks 1–13, the second trimester is weeks 14–27, and the third trimester is weeks 28–40 (or until delivery).