Baby Due Date Calculator by Week

Tracking your pregnancy by week is essential for understanding your baby's development and preparing for the arrival. Our baby due date calculator by week helps you determine your due date based on your last menstrual period (LMP) or ultrasound date.

How to Use This Calculator

Using our baby due date calculator is simple:

Enter your last menstrual period (LMP) date or ultrasound date
Select whether you're using LMP or ultrasound date
Click "Calculate" to see your estimated due date
Review the pregnancy timeline chart

Note: The average pregnancy lasts 40 weeks (280 days). Your due date is calculated by adding 40 weeks to your LMP date or using the ultrasound date as a reference point.

How the Due Date Calculation Works

The calculation is based on standard pregnancy guidelines:

Due Date = LMP Date + 280 days (40 weeks) OR Due Date = Ultrasound Date + (40 weeks - current pregnancy weeks)

For example, if your LMP was January 1, 2023, your due date would be October 31, 2023. If you had an ultrasound at 12 weeks, your due date would be April 11, 2023.

Understanding Pregnancy Weeks

Pregnancy is divided into three trimesters:

First trimester: Weeks 1-12 (conception to 3 months)
Second trimester: Weeks 13-26 (3-6 months)
Third trimester: Weeks 27-40 (6 months to birth)

The first day of your last menstrual period is considered week 1. Ultrasound dates are more precise as they count from the first day of the mother's last menstrual period.

Common Questions About Due Dates

Many expectant parents have questions about due dates. Here are some common concerns:

Can my due date change?

Yes, your due date can change if your pregnancy progresses faster or slower than expected. Ultrasounds can provide more accurate information about your baby's development.

What if I miss my period?

If you miss your period, you can use the first day of your missed period as your LMP date. If you're unsure, an ultrasound can confirm your due date.

How accurate is the due date calculator?

The calculator provides an estimate. For precise timing, consult your healthcare provider or use an ultrasound date.