Due Date Calculator

About Due Date Calculator

The due date calculator estimates when your baby will be born based on several methods. While only about 5% of women deliver on their exact due date, most deliver within a week before or after. The due date is typically calculated as 40 weeks (280 days) from the first day of your last menstrual period (LMP).

How Due Dates Are Calculated

There are three primary methods to estimate your due date:

1. Last Menstrual Period (LMP): The most common method adds 280 days (40 weeks) to the first day of your last period. This assumes a 28-day cycle with ovulation on day 14.
2. Conception Date: If you know your conception date, the calculator adds 266 days (38 weeks) to estimate the due date.
3. Ultrasound Dating: Early ultrasound measurements (especially in the first trimester) can provide the most accurate due date estimation by measuring the baby's size.

Pregnancy Trimesters

Pregnancy is divided into three trimesters:

• First Trimester: Week 1 to week 12 (months 1-3)
• Second Trimester: Week 13 to week 28 (months 4-6)
• Third Trimester: Week 29 to week 40 (months 7-9)

Important Milestones

Our calculator shows key pregnancy milestones including:

• Conception date (approximately 2 weeks after LMP)
• End of first trimester (12 weeks)
• End of second trimester (28 weeks)
• Full term (37-42 weeks)

Factors That Can Affect Due Date Accuracy

Several factors can influence the accuracy of your due date:

• Irregular menstrual cycles
• Variations in ovulation timing
• Incorrect recall of LMP date
• Variations in fetal growth rates

An early ultrasound (before 13 weeks) can help confirm or adjust your due date for greater accuracy.