Pregnancy Week Calculator

Find out how many weeks and days pregnant you are. Enter your LMP or due date to see your current pregnancy week instantly.

About the Pregnancy Week Calculator

Tracking your pregnancy week by week is essential for understanding fetal development, scheduling prenatal care, and preparing for each milestone. This calculator instantly tells you exactly how many weeks and days pregnant you are based on the first day of your last menstrual period.

Pregnancy is divided into 40 weeks from the LMP, and each week brings new developmental changes for your baby and physical changes for you. Knowing your exact week helps you follow along with pregnancy guides, understand what symptoms are normal, and ensure you schedule time-sensitive screenings like the nuchal translucency scan (weeks 11-14) or anatomy scan (weeks 18-22).

Whether you are in the early weeks of discovery or counting down the final days, this tool gives you a clear snapshot of where you are in your pregnancy journey. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation.

Why Use This Pregnancy Week Calculator?

Your pregnancy week determines everything from which prenatal tests are due to what size your baby is. Doctors, midwives, and pregnancy apps all reference your week of pregnancy. This calculator gives you the exact answer in seconds so you can stay informed and prepared for each stage of development. Having a precise figure at your fingertips empowers better planning and more confident decisions.

How to Use This Calculator

  1. Enter the first day of your last menstrual period (LMP).
  2. Alternatively, enter your estimated due date if you already know it.
  3. The calculator displays your current week and day of pregnancy.
  4. Review the trimester and progress percentage.
  5. Check back weekly to track your pregnancy progression.

Formula

weeks = floor((today − LMP) / 7) days = (today − LMP) mod 7 From due date: LMP = EDD − 280 days Then apply the same formula

Example Calculation

Result: 10 weeks, 1 day

If your LMP was December 1, 2025, and today is February 9, 2026, that is 71 days. Dividing by 7 gives 10 weeks and 1 day. You are in the first trimester and approximately 25% through your pregnancy.

Tips & Best Practices

Week-by-Week Milestones

Each week of pregnancy marks distinct developmental milestones. By week 8, all major organs have begun forming. By week 12, the risk of miscarriage drops significantly. Week 20 marks the halfway point, and by week 24, the baby reaches viability. Understanding your current week helps you appreciate these milestones and prepare for what comes next.

Importance of Accurate Dating

Accurate pregnancy dating ensures that time-sensitive tests and screenings happen at the right moments. The first-trimester combined screening (weeks 11-14), the anatomy scan (weeks 18-22), glucose tolerance test (weeks 24-28), and Group B strep screening (weeks 35-37) all depend on knowing your gestational age precisely.

Tracking Your Progress

Many expectant parents check their pregnancy week daily, especially in the early weeks. As you progress, each week feels like an achievement. This calculator provides a simple, bookmark-worthy way to check your exact week and see how far along you are in your pregnancy journey.

Frequently Asked Questions

How are pregnancy weeks counted?

Pregnancy weeks are counted from the first day of your last menstrual period (LMP), not from conception. This means in weeks 1-2 you are not actually pregnant yet — ovulation and conception typically occur in week 2-3.

What does 10w3d mean?

This notation means 10 weeks and 3 days of gestational age. It indicates you are in your 11th week of pregnancy (since counting starts at week 0). The "d" number ranges from 0 to 6.

Why does my app show a different week than my doctor?

This usually happens when the LMP dates differ. Your doctor may have adjusted the date based on an ultrasound, while your app may be using the original LMP. Update your app with the doctor-confirmed date.

When does each trimester begin?

The first trimester covers weeks 1-12, the second trimester weeks 13-27, and the third trimester weeks 28-40. These boundaries are standardized by ACOG and used by healthcare providers worldwide.

Is "weeks pregnant" the same as "weeks of pregnancy"?

Yes, they mean the same thing and refer to gestational age measured from the LMP. Both terms are used interchangeably in medical settings and pregnancy literature.

What if I'm past 40 weeks?

Going past 40 weeks is common — about 30% of pregnancies extend beyond the due date. Your provider will monitor you closely and may recommend induction between 41-42 weeks. The calculator will continue counting weeks accurately.

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