How Many Weeks Is My Baby Calculator Week by Week

How to Use This Calculator

To calculate your pregnancy week, you'll need either your last menstrual period (LMP) date or your ultrasound date. Enter the relevant date in the calculator on the right, then click "Calculate" to see your current pregnancy week.

Example Calculation

If your last menstrual period was on January 1, 2023, and today is March 15, 2023, you would calculate:

• From January 1 to March 15 is 64 days
• Divide by 7 to get weeks: 64 ÷ 7 ≈ 9.14 weeks
• Round to the nearest whole week: 9 weeks

This means your baby is approximately 9 weeks old.

Understanding Pregnancy Weeks

Pregnancy weeks are counted from the first day of your last menstrual period (LMP) or from the date of a confirmed ultrasound. The standard pregnancy lasts about 40 weeks (280 days).

Trimesters Overview

Baby Development Week by Week

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

First Trimester (Weeks 1-12)

• Week 1-2: Implantation, early organ formation
• Week 3-4: Heart begins to beat, limbs form
• Week 5-6: Face begins to form, eyes and ears develop
• Week 7-8: Baby can make facial expressions, fingers and toes form
• Week 9-12: Baby can hear sounds, eyes can detect light

Second Trimester (Weeks 13-26)

• Week 13-16: Baby can taste, hair grows, nails form
• Week 17-20: Baby can suck thumb, moves a lot, bones harden
• Week 21-24: Baby gains weight rapidly, lungs develop
• Week 25-26: Baby is fully formed, ready for birth

Third Trimester (Weeks 27-40)

• Week 27-28: Baby drops into pelvis, prepares for birth
• Week 29-32: Baby gains weight, fat stores for after birth
• Week 33-36: Baby's head engages in pelvis, amniotic fluid decreases
• Week 37-40: Baby is fully mature, ready for birth

Common Questions About Pregnancy Weeks

Here are answers to frequently asked questions about pregnancy weeks:

How is pregnancy measured in weeks?

Pregnancy is typically measured in weeks from the first day of your last menstrual period (LMP) or from the date of a confirmed ultrasound. The standard pregnancy lasts about 40 weeks (280 days).

What happens in each trimester?

The first trimester (weeks 1-12) is when the foundation of your baby is formed. The second trimester (weeks 13-26) is when your baby grows rapidly. The third trimester (weeks 27-40) focuses on preparing for birth.

When should I see a doctor during pregnancy?

You should see your doctor at your first prenatal appointment within the first few weeks of pregnancy. Regular checkups are recommended every 4 weeks until 28 weeks, then every 2 weeks until delivery.

What should I eat during pregnancy?

A balanced diet with plenty of fruits, vegetables, whole grains, lean proteins, and healthy fats is important during pregnancy. Avoid raw or undercooked foods, certain fish, and excessive caffeine.

When should I start prenatal vitamins?

Prenatal vitamins should be started before conception if possible, or as soon as pregnancy is confirmed. They continue throughout pregnancy and into postpartum.