Baby Pregnancy Due Date Calculator

Pregnancy due date is calculated based on the first day of your last menstrual period (LMP) or the date of a positive pregnancy test. This calculator helps you determine your estimated due date and understand key pregnancy milestones.

How to Use This Calculator

To calculate your baby's due date:

Enter the date of your last menstrual period (LMP) or the date of your positive pregnancy test.
Select whether you want to calculate based on LMP or the date of your positive test.
Click "Calculate" to see your estimated due date.

The calculator will display your estimated due date, the number of weeks pregnant, and important pregnancy milestones.

How Pregnancy Due Date is Calculated

Pregnancy is typically measured in weeks and days from the first day of your last menstrual period (LMP). The standard gestational period is 40 weeks (280 days).

Due Date = LMP Date + 280 days or Due Date = Positive Test Date + 266 days

For example, if your LMP was January 1, 2023, your due date would be October 31, 2023 (280 days later). If you had a positive test on January 1, 2023, your due date would be September 26, 2023 (266 days later).

Important Pregnancy Dates

Here are some key dates to remember during your pregnancy:

Weeks Pregnant	Milestone
1-4	Implantation and early development
5-8	Fetal organ formation
9-12	Facial features develop
13-16	Limbs and digits form
17-20	Fetal movement felt
21-24	Eyes and ears develop
25-28	Brain development accelerates
29-32	Lungs and digestive system mature
33-36	Fat stores accumulate
37-40	Final preparation for birth

Example Calculation

Let's say you had your last menstrual period on May 1, 2023. Using the calculator:

Enter May 1, 2023 as your LMP date.
Select "Last Menstrual Period" as the calculation method.
Click "Calculate".

The calculator will show that your estimated due date is February 1, 2024 (280 days after May 1, 2023).

This means you would be 40 weeks pregnant on February 1, 2024.

Frequently Asked Questions

What is the average length of pregnancy?: The average length of pregnancy is 40 weeks (280 days) from the first day of the last menstrual period.
How accurate is the due date calculator?: The due date calculator provides an estimate based on standard pregnancy length. Individual pregnancies may vary.
Can I use the date of a positive pregnancy test to calculate my due date?: Yes, you can use the date of your positive pregnancy test. The calculator will add 266 days to that date to estimate your due date.
What are some common pregnancy milestones?: Common pregnancy milestones include the development of organs, facial features, limbs, and fetal movement. The table in this guide shows key milestones by week.
When should I see a healthcare provider during pregnancy?: You should see a healthcare provider at your first prenatal visit, typically within the first 12 weeks of pregnancy. Regular checkups are recommended every 4 weeks until 28 weeks, then every 2-4 weeks until delivery.