Baby Due Date Weeks Calculator

Pregnancy is a journey that begins with the first day of your last menstrual period (LMP) and ends with the baby's due date. This calculator helps you determine your baby's due date in weeks by calculating from your LMP or from an ultrasound date.

How to Use This Calculator

To calculate your baby's due date in weeks:

Select whether you want to calculate from your last menstrual period (LMP) or from an ultrasound date.
Enter the date of your LMP or ultrasound date.
Click "Calculate" to see your due date and the number of weeks until then.

The calculator will show you:

Your estimated due date
The number of weeks until your due date
A chart showing your pregnancy timeline

How the Due Date Calculation Works

Pregnancy is typically considered to be 40 weeks long. The due date is calculated by adding 40 weeks to the first day of your last menstrual period (LMP).

Formula: Due Date = LMP Date + 40 Weeks

For example, if your LMP was on January 1, 2023, your due date would be on November 24, 2023.

If you have an ultrasound date, you can calculate your due date by adding the number of weeks since conception to the ultrasound date. Most ultrasound dates are calculated from the first day of the last menstrual period.

Note: The due date is an estimate. Your baby's actual delivery date may vary by a few days.

Example Calculation

Let's say your last menstrual period started on May 15, 2023. Here's how the calculation works:

Date	Description
May 15, 2023	First day of last menstrual period (LMP)
June 12, 2023	10 weeks since LMP
July 10, 2023	20 weeks since LMP
August 7, 2023	30 weeks since LMP
September 4, 2023	35 weeks since LMP
October 2, 2023	38 weeks since LMP
October 30, 2023	40 weeks since LMP (estimated due date)

Using this calculator, you can see that if your LMP was on May 15, 2023, your baby's due date would be October 30, 2023.

Tracking Pregnancy Weeks

Tracking your pregnancy weeks can help you stay informed about your baby's development. Here are some key milestones:

Weeks	Milestone
1-4	Implantation and early development
5-8	Organ formation begins
9-12	Fetal movement and heart activity
13-16	Limbs and facial features develop
17-20	Baby can hear and may respond to sound
21-24	Eyes open, hair grows, and baby can taste
25-28	Skin becomes less transparent, baby gains weight
29-32	Baby practices breathing, gains more weight
33-36	Baby is in a head-down position, ready for birth
37-40	Baby is fully developed and ready for delivery

This table provides a general overview of pregnancy milestones. Every pregnancy is unique, and these milestones may vary.

Frequently Asked Questions

How accurate is the due date calculation?

The due date calculation is an estimate based on the average length of pregnancy. Your actual delivery date may vary by a few days. Ultrasound dates are more accurate but still estimates.

Can I use this calculator if I had an ultrasound?

Yes, you can use the calculator with your ultrasound date. Most ultrasound dates are calculated from the first day of your last menstrual period, so you can enter that date to get an accurate due date.

What if I don't know my last menstrual period date?

If you don't know your LMP date, you can use an ultrasound date or your expected due date to calculate your pregnancy weeks.

How do I track my pregnancy weeks?

You can track your pregnancy weeks by counting from your LMP date or using an ultrasound date. Our calculator can help you visualize your pregnancy timeline.