When Will I Have My Baby Calculator

How to Use This Calculator

To estimate your due date, you'll need either:

• Your last menstrual period (LMP) date, or
• The date of your first-trimester ultrasound

Enter the relevant date in the calculator below and click "Calculate" to get your estimated due date. The calculator will also show you important pregnancy milestones based on your due date.

How the Due Date Calculation Works

The standard pregnancy length is 40 weeks (280 days) from the first day of your last menstrual period (LMP). The due date is calculated by adding 280 days to your LMP date.

If you have an ultrasound, the calculation is slightly different. The due date is calculated by adding the number of weeks since conception to the ultrasound date. For example, if your ultrasound shows your baby is 12 weeks old, you would add 12 weeks to the ultrasound date to get your due date.

How Accurate Is the Estimated Due Date?

The estimated due date (EDD) is based on your last menstrual period (LMP) or ultrasound date. It's important to remember that:

• The EDD is an estimate, not an exact prediction
• Pregnancy lengths can vary by several days
• Ultrasounds provide more accurate dates than LMP-based estimates

Pregnancy Timeline by Week

Here's a general overview of what to expect during each trimester of pregnancy:

First Trimester (Weeks 1-12)

• Weeks 1-2: Implantation and early development
• Weeks 3-4: Major organs begin to form
• Weeks 5-8: Baby's face, limbs, and heart begin to develop
• Weeks 9-12: Baby's movements become noticeable

Second Trimester (Weeks 13-26)

• Weeks 13-16: Baby gains most of their weight
• Weeks 17-20: Baby's bones harden
• Weeks 21-24: Baby's lungs mature
• Weeks 25-26: Baby's brain develops rapidly

Third Trimester (Weeks 27-40)

• Weeks 27-30: Baby's head drops into the pelvis
• Weeks 31-34: Baby's fat stores prepare for birth
• Weeks 35-37: Baby's lungs are fully mature
• Weeks 38-40: Baby is in the birth position