Pregnancy Week Calculator โ Track Your Baby's Growth Week by Week
Free pregnancy week calculator to track your current week and trimester. Enter your last period or conception date for instant results.
Pregnancy is a remarkable 40-week journey divided into three trimesters. Knowing exactly how far along you are helps you track your baby's development milestones; schedule prenatal appointments; and prepare for delivery. This calculator determines your current pregnancy week; trimester; and estimated due date based on your last menstrual period or known conception date.
How are pregnancy weeks counted?
Pregnancy weeks are counted from the first day of your last menstrual period (LMP); not from conception. This means you are technically 2 weeks pregnant at the time of conception. A full-term pregnancy is 40 weeks or 280 days from LMP. Doctors use this standardized method because LMP date is easier to pinpoint than the exact conception date.
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About This Health Metric
This calculator uses established medical formulas to estimate your health metrics. While these calculations provide useful benchmarks for general health monitoring, they are based on population averages and may not account for individual factors such as body composition, genetics, medical conditions, or fitness level. Athletes, pregnant women, and individuals with certain health conditions may get results that do not accurately reflect their actual health status. Always consult a healthcare professional for personalized medical advice.
Key Information
| Parameter | Details |
|---|---|
| Full Term Duration | 40 weeks (280 days from LMP) |
| First Trimester | Weeks 1-12 (major organ formation) |
| Second Trimester | Weeks 13-27 (rapid growth phase) |
| Third Trimester | Weeks 28-40 (final development and birth prep) |
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Use Calculator NowFrequently Asked Questions
How are pregnancy weeks counted?
Pregnancy weeks are counted from the first day of your last menstrual period (LMP); not from conception. This means you are technically 2 weeks pregnant at the time of conception. A full-term pregnancy is 40 weeks or 280 days from LMP. Doctors use this standardized method because LMP date is easier to pinpoint than the exact conception date.
What trimester am I in?
The first trimester covers weeks 1-12 and is when major organs form. The second trimester spans weeks 13-27; a period of rapid growth where you may feel your baby move. The third trimester is weeks 28-40; when the baby gains weight and prepares for birth. Most prenatal tests are scheduled around specific weeks within each trimester.
Is my due date accurate?
Only about 5% of babies are born on their exact due date. Most babies arrive within a 2-week window around the due date (between 38 and 42 weeks). First-time mothers tend to deliver slightly past their due date. An ultrasound in the first trimester provides the most accurate due date estimation; within about 5-7 days.
How accurate are online health calculators?
Online health calculators use established medical formulas and provide useful estimates for general guidance. However, individual factors like metabolism, medical conditions, and body composition can affect actual results. Always consult a healthcare professional for personalized advice.
What is a healthy BMI range?
BMI between 18.5-24.9 is normal weight. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is obese. BMI does not distinguish between muscle and fat, so athletes may show higher BMI without being overweight.
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Last updated: March 2026