Due Date: LMP 2025-01-01, 21-Day Cycle
Estimated due date for last menstrual period 2025-01-01 with 21-day cycle: Approximately 40 weeks from LMP. Free due date calculator.
Naegeles rule: LMP + 280 days + (21 - 28) = Approximately 40 weeks from LMP.
How This Was Calculated
Naegele's Rule (LMP):Due Date = LMP + 280 days + (Cycle Length - 28)
Conception Date:Due Date = Conception Date + 266 days (38 weeks)
IVF Transfer:Due Date = Transfer Date + (266 - Embryo Age in days)
Gestational Age:Weeks = Days from LMP / 7
Frequently Asked Questions
How accurate is a due date calculator?
Only about 4% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the estimated due date. First babies often arrive 1-2 weeks late.
Why is my due date different from my doctor's?
Doctors may use ultrasound measurements in early pregnancy to adjust dates. IVF due dates are typically more accurate than LMP-based dates because the exact conception date is known.
Can my due date change during pregnancy?
Yes, especially if your first ultrasound shows the baby is smaller or larger than expected for the gestational age. This is normal and helps ensure the most accurate due date.
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