Due Date Calculator
Enter the first day of your last period and your average cycle length to see your estimated due date, how far along you are today, and the milestones ahead.
Your dates
Your result
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Estimated due date
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Your 40-week timeline
Heartbeat ~8w
Anatomy scan ~20w
Full term 39w
You
1st trimester2nd trimester3rd trimester
Week 1Week 13Week 27Due · 40
Based on Naegele's rule (ACOG methodology). Estimates only — always confirm with your provider.
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How your due date is calculated
Doctors date pregnancy from the first day of your last menstrual period (LMP), not from conception. A full-term pregnancy averages 280 days (40 weeks) from the LMP — that's Naegele's rule. If your cycles run longer or shorter than 28 days, ovulation shifts too, so this calculator adds or subtracts the difference. Your provider may adjust the date after a first-trimester ultrasound, which is the most accurate dating method.