pregnancy calculator by weeks and months

How this pregnancy calculator by weeks and months works

Most pregnancy dating starts on the first day of your last menstrual period, not the day of conception. A full-term pregnancy is typically estimated at 40 weeks (280 days) from LMP for a 28-day cycle. If your cycle is usually longer or shorter, the estimated due date can shift slightly.

This calculator gives you:

• Your current gestational age in weeks and days
• Your estimated due date (EDD)
• Your current pregnancy month (approximate)
• Your trimester and key milestone dates

Weeks to months pregnancy chart

Many people ask, “How many months pregnant am I?” Clinics often use weeks, but this month guide can help:

• 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+

Month conversions are approximate because calendar months have different lengths.

Trimester breakdown

First trimester (weeks 1–13)

Early development is rapid. You may experience nausea, fatigue, breast tenderness, and frequent urination. Prenatal vitamins with folic acid are usually recommended during this phase.

Second trimester (weeks 14–27)

Energy often improves. Many parents begin to feel movement around weeks 18–22. Anatomy scans are commonly performed during this trimester.

Third trimester (weeks 28–40+)

Baby gains weight quickly and final organ maturation continues. You may notice stronger movement, sleep disruption, and increased pelvic pressure as birth approaches.

Why due dates can change

A due date is an estimate, not an exact prediction. Labor can naturally occur before or after the estimated date. Providers may refine dating using early ultrasound measurements, especially if cycle timing is uncertain.

• Only a small percentage of babies are born on the exact due date
• First pregnancies may run slightly longer
• Cycle irregularity can affect LMP-based dating

Frequently asked questions

How many weeks is 9 months pregnant?

In obstetrics, full term is around 40 weeks. “Nine months” is a simplified way to describe late pregnancy.

Can I calculate from conception date instead of LMP?

Yes, but conception date is often uncertain. LMP is commonly used because it is easier to track consistently.

What if my cycles are not regular?

Use this calculator as a rough estimate and discuss ultrasound dating with your provider for greater accuracy.

When to contact your healthcare provider

Reach out right away for severe abdominal pain, heavy bleeding, fluid leakage, fever, reduced fetal movement in later pregnancy, severe headache, vision changes, or any symptom that feels urgent to you.