Complete Guide: Understanding Pregnancy Trimesters
A trimester calculator breaks your full 40-week pregnancy into its three medically defined stages, so you know exactly when each one starts and ends. This free tool uses your last menstrual period (LMP) or due date to calculate precise start and end dates for each trimester.
💡 Quick Summary
A full-term pregnancy is divided into Trimester 1 (weeks 1-13), Trimester 2 (weeks 14-27), and Trimester 3 (week 28 to delivery, around week 40). Each trimester brings distinct symptoms, screenings, and developmental milestones.
The Three Trimesters at a Glance
| Trimester | Weeks | What Typically Happens |
|---|---|---|
| First Trimester | Weeks 1–13 | Major organ formation, morning sickness, first prenatal visit and dating scan |
| Second Trimester | Weeks 14–27 | Often called the "honeymoon" trimester; anatomy scan, feeling the baby move |
| Third Trimester | Week 28 to delivery | Rapid weight gain, more frequent checkups, preparing for labor and delivery |
Step-by-Step Instructions
- Select whether you're entering your LMP date or your due date.
- Enter the date using the date picker.
- Click ⚡ Calculate My Trimesters.
- Review the exact start and end dates for each trimester and your current stage.
- Use the 📋 Copy Summary button to save your results.