Due Date Calculator
Enter your last period or conception date to estimate your due date, current week, and trimester milestones.
Enter a date to see results
How Does the Due Date Calculator Work?
This calculator uses Naegele's rule — the same formula used by OB-GYNs worldwide. It adds 280 days (40 weeks) to the first day of your last menstrual period, adjusted for your cycle length. If you know your conception date, it adds 266 days (38 weeks) instead.
How Accurate Is a Due Date?
Only about 5% of babies are born on their exact estimated date. Most babies arrive within 2 weeks before or after the due date. Your doctor may adjust the date based on a first-trimester ultrasound, which is generally more accurate than LMP-based calculation.
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Frequently Asked Questions
This tool provides general guidance and is not medical advice. Always consult your pediatrician.
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