What if my cycle is longer or shorter than 28 days?

Adjust using the cycle length field. Longer cycles mean ovulation occurs later, so we add those extra days to calculations. For a 35-day cycle, add 7 days to standard calculations.

When do the trimesters begin and end?

First trimester: weeks 1-12. Second trimester: weeks 13-26. Third trimester: weeks 27-40. Each has distinct developmental milestones and common symptoms.

Is my due date exact?

Only about 5% of babies arrive on their due date. It's an estimate—full term is 37-42 weeks. Your healthcare provider may adjust based on ultrasound measurements.

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Pregnancy Week Calculator

Calculate your current pregnancy week, trimester, due date, and track your pregnancy progress

Last Menstrual Period (LMP)

Cycle Length

days

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Track Your Pregnancy Week by Week

Know exactly where you are in your pregnancy journey. This calculator determines your current pregnancy week, shows which trimester you're in, calculates your due date, and tracks your progress toward delivery day.

Understanding Pregnancy Weeks

Pregnancy is measured from the first day of your last menstrual period (LMP), even though conception occurs about 2 weeks later. A full-term pregnancy is 40 weeks. The first trimester (weeks 1-12) involves rapid cell division. The second trimester (weeks 13-26) brings major organ development. The third trimester (weeks 27-40) focuses on growth and preparation for birth.

Pregnancy Week Calculation

Weeks = (Today - LMP) ÷ 7

How to Use This Calculator

Using Your Pregnancy Week Information

Prenatal Care Planning

Know when to schedule glucose tests, anatomy scans, and other milestone appointments.

Baby Development Tracking

Each week brings new developments—learn what's happening with your baby.

Preparing for Baby

Use trimester milestones to plan nursery setup, baby shopping, and birth preparation.

Frequently Asked Questions

Most women know their LMP date but not conception date. Since ovulation typically occurs 14 days after LMP in a 28-day cycle, this method provides a consistent starting point for dating pregnancy.