Due Date Calculator
Calculate your pregnancy due date using LMP or conception date with Naegele's rule
Calculate Your Due Date
Enter the first day when your last period started
Typical range is 21-35 days (average 28 days)
Medical Disclaimer
This calculator provides estimates only. Only about 4% of babies are born exactly on their due date. Always consult with your healthcare provider for accurate pregnancy dating and medical care.
Calculation Methods
Naegele's Rule (LMP)
LMP + 280 days + cycle adjustment
Conception Date
Conception + 266 days
Pregnancy Trimesters
1st Trimester
Weeks 1-12
Organ development begins
2nd Trimester
Weeks 13-28
Most comfortable period
3rd Trimester
Weeks 29-40
Rapid growth and preparation
Important Notes
Only 4% of babies are born on exact due date
Full-term is 37-42 weeks
80% born within ±2 weeks of due date
Regular prenatal care is essential
Understanding Due Date Calculation
Naegele's Rule (LMP Method)
The most common method adds 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14. The formula adjusts for different cycle lengths.
Why 280 Days?
- •Based on average pregnancy length from LMP
- •Includes ~2 weeks before conception
- •Standard medical dating convention
Conception Date Method
If you know the exact conception date, this method adds 266 days (38 weeks) to that date. This is more accurate for women with irregular cycles or those who track ovulation.
Accuracy Considerations
- •Ultrasound dating may be more accurate
- •Early ultrasound (6-11 weeks) is most precise
- •Multiple factors affect actual delivery date
Example Calculation
LMP Method
Last period: January 1, 2024
Cycle length: 28 days
Due date: October 8, 2024
(Jan 1 + 280 days)
Conception Method
Conception: January 15, 2024
Due date: October 8, 2024
(Jan 15 + 266 days)