Pregnancy Week Calculator — Free 2026
Find your current pregnancy week, trimester, and baby size from your due date or LMP.
How It Works
- Choose input method
- Enter the date
- View your results
Understanding Pregnancy Weeks
Pregnancy is typically measured from the first day of your last menstrual period (LMP), even though conception usually occurs about two weeks later. A full-term pregnancy lasts approximately 280 days or 40 weeks from LMP. This calculator uses the widely accepted Naegele's rule to estimate your due date and determine your current gestational week.
Trimesters Explained
The first trimester (weeks 1-12) is when major organs begin forming. The second trimester (weeks 13-27) is often called the "golden period" as morning sickness typically eases and the baby grows rapidly. The third trimester (weeks 28-40) is when the baby gains weight and prepares for birth. Each trimester brings different physical changes and developmental milestones. For a full due date estimate, try our pregnancy due date calculator.
Baby Size Comparisons
We compare your baby's size to familiar fruits and vegetables at each stage. At 8 weeks, the embryo is roughly the size of a raspberry. By 20 weeks, the baby is about the length of a banana. At 40 weeks, your baby is approximately the size of a small watermelon. These comparisons help you visualize growth in a fun, relatable way.
When to See Your Doctor
This tool provides general estimates based on standard medical guidelines. Every pregnancy is unique. Your healthcare provider may adjust your due date based on ultrasound measurements, especially in the first trimester. Always attend your scheduled prenatal appointments and discuss any concerns with your doctor. You can also track your overall health metrics with our BMI calculator.
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