Pregnancy Week Calculator — How Many Weeks Pregnant Am I?
Find out exactly how many weeks and days pregnant you are with our gestational age calculator. Track your pregnancy progress from your last period.
Calculate Your Pregnancy Week
What Is a Pregnancy Week Calculator?
How It Works
A pregnancy week calculator determines your gestational age by counting the days from the first day of your last menstrual period (LMP) and dividing by seven. This gives you the precise number of weeks and days you are pregnant. The calculation follows the same medical standard used by obstetricians worldwide. Simply enter your LMP date and our tool instantly provides your current pregnancy week, trimester, estimated due date, and days remaining until delivery. This information is fundamental for tracking your baby's development against established milestones.
Why It Is Important
Knowing exactly how many weeks pregnant you are is crucial for proper prenatal care. Your healthcare provider uses this information to schedule important tests and screenings at the right time, such as the first-trimester screening, anatomy scan, and glucose tolerance test. Each pregnancy week corresponds to specific developmental milestones for your baby, and understanding where you are in the timeline helps you know what to expect, what symptoms are normal, and when to seek medical attention. The pregnancy week calculator provides the foundation for informed pregnancy management.
Pregnancy Week-by-Week Development Milestones
Week 4
Implantation
The embryo implants in the uterine lining. The placenta begins to form, and hCG production starts. A pregnancy test may show positive results.
Week 8
Heartbeat Begins
The baby's heart begins beating at about 150-170 beats per minute. Arms and legs are forming, and facial features start to develop.
Week 12
End of First Trimester
All major organs have formed. The baby is about 2.5 inches long. Risk of miscarriage drops significantly. Morning sickness may begin to ease.
Week 16
Quickening
Some women begin to feel baby's first movements. The baby can make facial expressions and has fully formed fingernails.
Week 20
Halfway Point
Anatomy scan ultrasound reveals baby's development in detail. The baby is about 10 inches long and can hear sounds from outside the womb.
Week 24
Viability Milestone
The baby reaches a major viability milestone. Lungs are developing rapidly. With medical intervention, babies born at this stage have a chance of survival.
Week 28
Third Trimester
Baby's eyes open and close. Brain development accelerates. The baby begins to gain weight rapidly and the kicks become more noticeable.
Week 36
Early Term
Baby's lungs are nearly mature. The head may engage in the pelvis. Most babies are in the head-down position preparing for birth.
Week 40
Full Term
Your due date has arrived! The average baby weighs about 7.5 pounds. Only 5% of babies arrive exactly on their due date — most come within two weeks.
Understanding the Three Trimesters
First Trimester
Weeks 1-12
Common Symptoms
- Morning sickness and nausea
- Breast tenderness and swelling
- Fatigue and increased sleep need
- Frequent urination
- Food cravings or aversions
- Mood swings from hormonal changes
Tips
- Take prenatal vitamins with folic acid daily
- Eat small frequent meals to manage nausea
- Stay hydrated throughout the day
- Get plenty of rest when your body demands it
Second Trimester
Weeks 13-26
Common Symptoms
- Growing belly and weight gain
- Baby movements become noticeable
- Back pain begins
- Stretch marks may appear
- Braxton Hicks contractions start
- Increased appetite
Tips
- Start sleeping on your left side
- Wear supportive maternity clothing
- Attend your anatomy scan at 20 weeks
- Begin gentle pregnancy exercises
Third Trimester
Weeks 27-40
Common Symptoms
- Shortness of breath as uterus grows
- Swelling in feet and ankles
- Frequent urination returns
- Difficulty sleeping comfortably
- Stronger and more frequent kicks
- Nesting instinct intensifies
Tips
- Pack your hospital bag by week 36
- Finalize your birth plan with your doctor
- Practice breathing and relaxation techniques
- Prepare the nursery and baby essentials
Gestational Age vs Fetal Age: What Is the Difference?
Gestational Age
Gestational age is the medical standard for measuring pregnancy duration. It starts counting from the first day of your last menstrual period, which is typically about two weeks before conception actually occurs. When your doctor tells you that you are 20 weeks pregnant, they are referring to gestational age.
- Measured from LMP date (about 2 weeks before conception)
- Standard used by all healthcare providers globally
- Pregnancy is 40 weeks (280 days) from LMP at full term
- Used to schedule all prenatal tests and appointments
- The basis for pregnancy week calculator results
Fetal (Conceptional) Age
Fetal age measures the actual time since conception. Since conception typically occurs around day 14 of the cycle, fetal age is about 2 weeks less than gestational age. Some developmental resources and international pregnancy guides use fetal age instead.
- Measured from the actual date of conception
- About 2 weeks less than gestational age at any point
- Reflects the actual developmental age of the fetus
- Full-term pregnancy is 38 weeks from conception
- May cause confusion when comparing with gestational references
Prenatal Visit Schedule by Pregnancy Week
Week 6-8
Initial Visit
Pregnancy confirmation, blood tests, health history review, and initial physical exam. Your doctor will calculate your due date and begin your prenatal record.
Week 8-12
First Trimester Screening
Blood tests for genetic conditions, first ultrasound to confirm viability and dates. Optional NIPT (non-invasive prenatal testing) may be offered at this time.
Week 16-20
Second Trimester Check
Quad screen blood test for genetic markers. Your doctor checks fundal height, heartbeat, and reviews any symptoms. Preparing for the anatomy scan.
Week 18-22
Anatomy Scan
Detailed ultrasound examining baby's organs, growth, and development. May reveal the baby's sex if desired. This is one of the most important prenatal screenings.
Week 24-28
Glucose Test
Glucose tolerance test to screen for gestational diabetes. RhoGAM injection if Rh-negative. Regular checkups become more frequent from this point forward.
Week 36-40
Final Weeks
Weekly visits with cervical checks. Group B strep test at 36 weeks. Birth plan review and labor signs education. Your baby is considered early term at 37 weeks.
Important Pregnancy Week Facts
40 Weeks Total
A full-term pregnancy lasts 40 weeks from the last menstrual period, though most babies arrive between 38-42 weeks.
3 Trimesters
Pregnancy is divided into three 13-14 week trimesters, each with unique developmental milestones and maternal changes.
Week 24 Viability
Week 24 is considered the viability milestone. Babies born at this stage have a chance of survival with intensive medical care.
Week 20 Halfway
Week 20 marks the halfway point of pregnancy. The anatomy scan ultrasound provides detailed views of your baby's development.