Pregnancy Due Date Calculator
Calculate your estimated due date based on your last menstrual period or conception date. See a full pregnancy timeline with trimester milestones.
Part of our Health Calculators collection.
Pregnancy Due Date Calculator
Free online calculator
First day of last period, or conception date
Only used for LMP method
Results update automatically as you type
How to Use This Calculator
- 1
Select whether you know your last menstrual period date or conception date.
- 2
Enter the date.
- 3
See your estimated due date, current pregnancy week, and trimester.
- 4
Use the timeline to track upcoming milestones.
How Due Date is Calculated
LMP Method: Due Date = LMP + 280 days (40 weeks) Conception Method: Due Date = Conception Date + 266 days (38 weeks) The Naegele's Rule formula: LMP + 1 year − 3 months + 7 days Only ~5% of babies are born on their exact due date. A full-term birth is 37–42 weeks.
Example Calculation
Example: LMP on January 1, 2025
Inputs
Result
Due Date: October 8, 2025
January 1 + 280 days = October 8, 2025. Roughly: January → subtract 3 months (October) + add 7 days (8th).
Understanding Your Due Date
Your estimated due date (EDD) is calculated by adding 280 days to the first day of your last menstrual period. This assumes a standard 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, your doctor may adjust the date. The most accurate way to confirm your due date is an early ultrasound between 8 and 12 weeks, which measures the baby's size directly.