Pregnancy Week Calculator

About the Pregnancy Week Calculator

Pregnancy advice, appointment timing, and fetal-development updates are usually organized by gestational week, not by month. This calculator tells you exactly how many weeks and days pregnant you are based on your LMP or due date.

That matters because screening windows are narrow. A nuchal translucency scan, anatomy scan, glucose test, and Group B strep screen all depend on being in the right week range. The same is true for reading pregnancy guides and understanding what symptoms or milestones are common at a given point.

Use it as a quick reference when you want the exact week-and-day format your provider and ultrasound reports use.

When This Page Helps

Your current pregnancy week affects screening timing, fetal-growth expectations, symptom guides, and how providers document progress. A clear week-and-day answer is more useful than saying you are "about two and a half months" pregnant, especially when appointments and tests are time-sensitive.

How to Use the Inputs

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.

Example Calculation

Tips & Best Practices

• Pregnancy weeks start from week 0 — you are in "week 1" during days 0-6 after LMP.
• Your provider counts pregnancy from the LMP, so you are technically "pregnant" two weeks before conception.
• Weeks 1-12 are the first trimester, 13-27 the second, and 28-40 the third.
• Key screening windows are week 11-14 (nuchal translucency) and week 18-22 (anatomy scan).
• If your LMP date was adjusted by ultrasound, use the adjusted LMP for accuracy.
• Pregnancy apps and books reference gestational age — This calculator gives the same number.

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. It gives 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.