Baby Due Date Calculator Week by Week

Tracking your pregnancy week by week is an exciting journey. Our baby due date calculator helps you understand each stage of development by showing you the due date and key milestones for every week of pregnancy.

How to Use This Calculator

To use the baby due date calculator:

Enter your last menstrual period (LMP) date or estimated due date (EDD)
Select whether you're calculating from LMP or EDD
Click "Calculate" to see your pregnancy timeline
View the week-by-week breakdown and key milestones

The calculator shows your estimated due date, current week of pregnancy, and important developmental milestones for each week.

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.

Due Date = LMP Date + 280 days Current Week = (Today's Date - LMP Date) / 7

For example, if your LMP was January 1, 2023, your due date would be October 31, 2023 (280 days later). If today is May 1, 2023, you would be in week 16 of pregnancy.

Note: Due dates are estimates. Your actual delivery date may vary by several days.

Week-by-Week Pregnancy Timeline

Each week of pregnancy brings new developments. Here's a brief overview of what happens during each stage:

Week	Key Developments
1-4	Implantation, early organ formation, rapid cell division
5-8	Limbs forming, heart begins to beat, facial features developing
9-12	Eyes, ears, and nose forming, fingers and toes developing
13-16	Fingernails and toenails forming, baby can hear sounds
17-20	Eyes can see light, baby's skin forms, hair grows
21-24	Baby can swallow, lungs developing, fat stores building
25-28	Baby can taste, practice breathing, moves frequently
29-32	Lungs mature, baby gains weight rapidly, ready for birth
33-36	Baby is in "active survival mode," ready for delivery
37-40	Baby is fully developed, ready for birth

Common Questions About Due Dates

Here are answers to frequently asked questions about pregnancy due dates:

Why are due dates estimates?: Due dates are based on averages. Each pregnancy is unique, and delivery dates can vary by several days.
What if my due date changes?: If your doctor determines your due date is inaccurate, they may adjust it based on ultrasound measurements.
Can I find out my baby's due date early?: Yes, a first-trimester ultrasound can provide a more accurate due date around 10-13 weeks.
What if I'm pregnant with twins?: Twins typically have a due date about 2 weeks earlier than a singleton pregnancy.
Should I trust my due date completely?: Use your due date as a general guideline, but always follow your doctor's advice about when to expect delivery.