Due Date Calculator
Calculate your estimated due date from your last menstrual period or conception date. Get your complete pregnancy timeline.
How Due Date is Calculated
The most common method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle. If your cycle is longer or shorter, the calculator adjusts accordingly.
Methods of Calculation
From LMP: Due Date = LMP + 280 days + (cycle – 28) days adjustment.
From Conception: Due Date = Conception Date + 266 days (38 weeks from fertilization).
What if My Due Date Changes?
Your doctor may adjust your due date after an early ultrasound (before 13 weeks), which is considered the most accurate method for dating a pregnancy.
FAQs
How accurate is the due date?
Only about 4% of babies arrive on the exact due date. Most arrive within 2 weeks of the estimated date.
Can I go into labor before my due date?
Yes. Anything from 37 weeks is considered full-term. Preterm birth is before 37 weeks.
What if I have irregular cycles?
Use your best estimate of cycle length, or use a conception date if known. An early ultrasound gives the most accurate dating.