Pregnancy Calculator

Calculation Methods Explained

Pregnancy dating can be done in several ways. Our calculator supports the most common medical methods:

• Last Period (LMP): The standard method. Adds 280 days to the first day of your last menstrual period. Adjusts for cycle length.
• Conception Date: If you know exactly when you conceived (ovulation), we add 266 days (38 weeks) to find your due date.
• Ultrasound: Early ultrasounds are very accurate for dating. Enter the date of the scan and the measurements (weeks/days) given by the sonographer.
• IVF Transfer: Calculated based on the transfer date and the age of the embryo (Day 3 or Day 5) to provide a precise medical due date.

Understanding Gestational Age

You might be confused why you are considered "4 weeks pregnant" when you likely conceived only 2 weeks ago. Doctors count pregnancy weeks from the first day of your last period, not the date of conception. This is because the LMP is a reliable, observable date.

So, in the first 2 weeks of your "pregnancy," you weren't actually pregnant yet—your body was preparing for ovulation!

Trimester Breakdown

• First Trimester (Weeks 1-12): Early development, organ formation, and highest risk of miscarriage.
• Second Trimester (Weeks 13-27): Often called the "honeymoon phase." Baby grows rapidly, movement can be felt, and gender is determinable.
• Third Trimester (Weeks 28-40+): Final growth, lung maturation, and preparation for labor.