pregnancy month calculator by weeks - Aaron Graves, PhDude Replica

Pregnancy Month Calculator (By Weeks)

Enter your pregnancy week and day, or enter your LMP date. The calculator will estimate your current month of pregnancy, trimester, and due date.

Pregnancy Week

Additional Days Use days in addition to weeks (for example: 24 weeks + 3 days).

OR Last Menstrual Period (LMP) Date If provided, LMP date is used to calculate gestational age automatically.

How to Convert Pregnancy Weeks to Months

Pregnancy is most accurately tracked in weeks, but many people naturally think in months. A full-term pregnancy is usually about 40 weeks, counted from the first day of your last menstrual period (LMP). Because calendar months have different lengths, week-to-month conversion is always an approximation.

This calculator gives you a practical month estimate used in common prenatal conversations. It does not replace your provider’s official dating scan or clinical timeline.

Pregnancy Month-by-Week Chart

Month 1: Weeks 1–4
Month 2: Weeks 5–8
Month 3: Weeks 9–13
Month 4: Weeks 14–17
Month 5: Weeks 18–22
Month 6: Weeks 23–27
Month 7: Weeks 28–31
Month 8: Weeks 32–35
Month 9: Weeks 36–40+

Trimester Breakdown

First trimester: 0 weeks to 13 weeks + 6 days
Second trimester: 14 weeks to 27 weeks + 6 days
Third trimester: 28 weeks to birth

How This Calculator Works

Option 1: You Know Your Current Week

If your care team already told you your gestational age (for example, 21 weeks 2 days), enter it directly. The calculator maps that age to a pregnancy month and estimates your due date relative to today.

Option 2: You Know Your LMP Date

If you enter the first day of your last menstrual period, the tool calculates how many days have passed up to today, converts that into weeks and days, and then estimates your due date using a 280-day pregnancy length.

Important: Due dates are estimates. Many healthy pregnancies deliver before or after the estimated due date. Your obstetrician or midwife has the final say based on ultrasound and clinical history.

Example Conversion

If you are 26 weeks 4 days pregnant:

You are in the second trimester
You are approximately in month 6
You are getting closer to the third trimester milestone at 28 weeks

Why Weeks Matter More Than Months

Prenatal milestones are tied to weeks, not months. Screening windows, anatomy scans, growth checks, and treatment timing all depend on precise gestational age. That is why clinics speak in weeks and days, even when friends and family ask, “What month are you in?”

Frequently Asked Questions

Is pregnancy exactly 9 months?

Not exactly. Forty weeks is closer to 9 months plus about 1 week. That’s why month-based tracking is approximate.

Can my due date change?

Yes. Early ultrasound can refine or adjust your expected due date, especially if ovulation happened earlier or later than average.

What if I am past 40 weeks?

The calculator will still classify you in month 9 and show you as overdue. Contact your provider for personalized guidance and monitoring.

Final Thoughts

Use this pregnancy month calculator by weeks for a quick, practical estimate of where you are in pregnancy. It is ideal for planning, tracking milestones, and understanding trimester transitions. For any medical decisions, always rely on your prenatal care team.