Pregnancy Weeks & Due Date Calculator
Your Pregnancy Results
How to Calculate How Many Weeks Pregnant You Are
Calculating your pregnancy weeks is the first step in tracking your baby's development and planning for your future. While it might seem straightforward, the medical community uses a specific method called the LMP (Last Menstrual Period) method.
The LMP Method Explained
Most pregnancies last approximately 40 weeks (280 days). Since the exact moment of conception is often difficult to determine, doctors count pregnancy from the first day of your last menstrual period. This means that during your first two weeks of "pregnancy," you weren't actually pregnant yet—your body was preparing for ovulation!
Adjusting for Cycle Length
The standard "Naegele's Rule" assumes a perfect 28-day menstrual cycle with ovulation occurring on day 14. However, many women have shorter or longer cycles. Our calculator allows you to input your average cycle length to provide a more accurate estimated due date (EDD).
- First Trimester: Weeks 1 to 12
- Second Trimester: Weeks 13 to 26
- Third Trimester: Weeks 27 to 40+
Real-World Examples
Example 1: If your last period started on January 1st and you have a 28-day cycle, on February 12th, you would be 6 weeks and 0 days pregnant. Your due date would be October 8th.
Example 2: If you have a longer 32-day cycle, your ovulation likely happened later. The calculator adds those extra 4 days to your due date calculation, ensuring more accuracy than a standard calendar wheel.
Why Does My Week Count Matter?
Knowing your exact week helps healthcare providers monitor milestones such as the first heartbeat (usually around week 6), the anatomy scan (around week 20), and glucose screening (around week 24-28). It also helps determine if your baby is growing at a healthy rate according to gestational age charts.