Pregnancy Week Calculator

Find out how many weeks pregnant you are and track your baby's development journey.

Calculate Your Pregnancy Week

Find out how far along you are in your pregnancy.

First Day of Last Menstrual Period

This is the most common method used by healthcare providers.

How pregnancy weeks are counted: Pregnancy is dated from the first day of your last menstrual period (LMP), even though conception typically occurs about 2 weeks later. This means you're already "2 weeks pregnant" at conception.

A full-term pregnancy is 40 weeks (280 days) from LMP, or 38 weeks (266 days) from conception.

How Pregnancy Weeks Are Calculated

Pregnancy is typically dated from the first day of your last menstrual period (LMP), not from the date of conception. This may seem counterintuitive, but it's the standard method used by healthcare providers worldwide because:

Most women know when their last period started
The exact date of conception is often unknown
It provides a consistent starting point for all pregnancies

This means that when you conceive (about 2 weeks after your LMP), you're already considered "2 weeks pregnant."

The Three Trimesters

First Trimester

Weeks 1-12

Major organs begin forming. Morning sickness is common. Risk of miscarriage is highest. The heart begins to beat around week 6.

Second Trimester

Weeks 13-26

Often the most comfortable period. You'll feel baby movement. Gender can be determined. Energy levels typically improve.

Third Trimester

Weeks 27-40

Baby gains weight rapidly. Braxton Hicks contractions may occur. Baby moves into head-down position for birth.

Important Pregnancy Milestones

Week 4-5: Pregnancy test becomes positive
Week 6-7: Heartbeat can be detected on ultrasound
Week 12: End of first trimester, reduced miscarriage risk
Week 16-20: You may feel first movements (quickening)
Week 18-22: Anatomy scan ultrasound
Week 24: Viability milestone - baby could survive if born early
Week 37: Considered full term
Week 40: Due date

Due Date Accuracy

Only about 5% of babies are born on their exact due date. Most babies arrive within two weeks before or after the due date. Your healthcare provider may adjust your due date based on:

Early ultrasound measurements (most accurate)
Physical examination findings
IVF transfer date (if applicable)

A pregnancy is considered full-term between weeks 39 and 40, early-term between weeks 37 and 38, and post-term after week 42.

When to See Your Healthcare Provider

As soon as you have a positive pregnancy test
If you experience bleeding or severe cramping
If you have concerns about your symptoms
For regular prenatal checkups as recommended