BabyDateCalc

Pregnancy Weeks to Months Converter

Easily convert your pregnancy weeks into months and trimesters. See exactly where you are in your pregnancy journey with our visual timeline.

Enter Pregnancy Week
Select your current pregnancy week (1-42) to see the equivalent month and trimester.
Week 1Week 14Week 28Week 42
Results

Current Week

Week 12

Month

Month 3

Week 4 of 5 in this month

Trimester

1st Trimester
Pregnancy Timeline
Your current position across all three trimesters

1st Trimester

(Weeks 1-13)Current

2nd Trimester

(Weeks 14-27)

3rd Trimester

(Weeks 28-42)
Month-by-Month Reference
Month 1

Weeks 1-4

1st Trimester
Month 2

Weeks 5-8

1st Trimester
Month 3You are here

Weeks 9-13

1st Trimester
Month 4

Weeks 14-17

2nd Trimester
Month 5

Weeks 18-22

2nd Trimester
Month 6

Weeks 23-27

2nd Trimester
Month 7

Weeks 28-31

3rd Trimester
Month 8

Weeks 32-35

3rd Trimester
Month 9

Weeks 36-40

3rd Trimester

How It Works

Our weeks to months converter uses a standardized pregnancy month mapping that healthcare providers commonly reference. Since pregnancy months don't align perfectly with calendar months (a month averages 4.3 weeks, not 4), the converter uses the widely accepted week-to-month breakdown:

  • First Trimester (Months 1-3): Weeks 1 through 13, covering early development from implantation through organ formation.
  • Second Trimester (Months 4-6): Weeks 14 through 27, when baby grows rapidly and movements become noticeable.
  • Third Trimester (Months 7-9): Weeks 28 through 40+, focused on baby's weight gain and lung maturation.

Simply enter or slide to your current pregnancy week to instantly see which month and trimester you are in, along with a visual timeline showing your position across all three trimesters.

Frequently Asked Questions

How do pregnancy weeks convert to months?

Pregnancy months don't align perfectly with calendar months. Generally: Month 1 covers weeks 1-4, Month 2 is weeks 5-8, Month 3 is weeks 9-13, Month 4 is weeks 14-17, Month 5 is weeks 18-22, Month 6 is weeks 23-27, Month 7 is weeks 28-31, Month 8 is weeks 32-35, and Month 9 is weeks 36-40.

Why is pregnancy counted as 40 weeks but only 9 months?

Pregnancy is measured from the first day of your last menstrual period (LMP), which is about 2 weeks before conception actually occurs. This means the 40-week count includes roughly 2 weeks when you weren't actually pregnant. Additionally, calendar months average about 4.3 weeks, not exactly 4, which accounts for the seeming discrepancy.

What are the three trimesters of pregnancy?

The first trimester spans weeks 1-13, the second trimester covers weeks 14-27, and the third trimester runs from week 28 until birth (typically around week 40). Each trimester brings different developmental milestones and physical changes.

Is there a 10th month of pregnancy?

Some people consider weeks 40-42 as a '10th month,' since 40 weeks is technically longer than 9 calendar months. However, medically, pregnancy is divided into 9 months across 3 trimesters, with weeks 36-40+ considered the ninth month.

Medical Disclaimer

This calculator is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider for medical decisions regarding your pregnancy.