Pregnancy Calculator
Calculate pregnancy milestones, trimester dates, and current week based on your last menstrual period (LMP).
How pregnancy weeks are counted.
Pregnancy is measured from the first day of your last menstrual period (LMP). A full-term pregnancy is 40 weeks (280 days).
Tracking Your Pregnancy Week by Week
Pregnancy is a remarkable 40-week journey marked by rapid physiological shifts and baby development. A pregnancy calculator helps expectant parents understand what is happening inside the womb at each stage. By monitoring gestational milestones, you can better prepare for prenatal visits, learn about body changes, and connect with your child's growth step by step.
Understanding Gestational Weeks & Trimesters
Clinically, pregnancy is measured from the first day of your last menstrual period (LMP) rather than the date of conception, because the exact conception date is rarely known. This means that during weeks 1 and 2, you are not technically pregnant yet—your body is preparing for ovulation. The 40 weeks are divided into three trimesters: the First Trimester (weeks 1–12) is the critical organ development phase; the Second Trimester (weeks 13–26) is the growth and movement phase; and the Third Trimester (weeks 27–40) is the weight gain and preparation phase.
Critical Gestational Milestones
Throughout pregnancy, key milestones mark the baby's development. By week 5, the neural tube is forming; by week 9, the heart is beating and limbs are developing; by week 20, you reach the midpoint and can feel the baby move (quickening); and by week 37, the baby is considered early-term, with fully developed lungs. Tracking these milestones helps you stay informed and discuss progress accurately with your obstetrician or midwife.
Frequently Asked Questions
Your gestational age in weeks is calculated from the first day of your Last Menstrual Period (LMP). For example, if your LMP was 10 weeks ago, you are considered 10 weeks pregnant. Note that conception typically occurs around week 2–3, so gestational age is 2 weeks more than the actual age of the embryo.
Gestational age counts from the LMP date and is the standard used by obstetricians worldwide. Embryonic age (also called fetal age) counts from the date of fertilization, which is typically 2 weeks after the LMP. Most pregnancy milestones, scan reports, and week-by-week guides use gestational age.
The first trimester spans weeks 1–13 and covers early organ development. The second trimester is weeks 14–26, when the baby grows rapidly and movement is first felt. The third trimester is weeks 27–40, during which the baby gains most of its weight and prepares for birth. Full term is 39–40 weeks 6 days.
The first prenatal visit is typically scheduled between 6 and 10 weeks of pregnancy. At this appointment, your OB or midwife will confirm the pregnancy, estimate your due date, check vital signs, order initial blood tests, and may perform an early ultrasound. Early prenatal care is associated with better outcomes for both mother and baby.
No. This calculator is an educational tool based on standard obstetric guidelines. It does not account for irregular cycles, multiple pregnancies, IVF, or medical complications. Always consult a certified obstetrician or midwife to confirm your due date, monitor your pregnancy, and address any health concerns.