Trimester Calculator
Find out which trimester you're in and what to expect.
The standard starting point for gestational age.
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Enter your last menstrual period or due date to find out exactly which trimester you are in, with your trimester start and end dates, how many weeks remain in the current trimester, and what to expect at each stage of pregnancy.
Frequently asked questions
How long is each trimester?
Each trimester lasts approximately 13 weeks. The first trimester is weeks 1–12, the second trimester is weeks 13–26, and the third trimester runs from week 27 to birth (typically week 40).
What happens in the first trimester?
Your baby's major organs and structures form during the first trimester. Common symptoms include morning sickness, fatigue, tender breasts, and frequent urination. Your first prenatal appointment and early scans usually happen during this time.
What happens in the second trimester?
Often called the golden trimester, weeks 13–26 typically bring more energy and less nausea. You'll likely feel your baby move for the first time (quickening), and the 20-week anatomy scan takes place during this period.
What happens in the third trimester?
Your baby grows rapidly and moves into position for birth. Common symptoms include back pain, heartburn, swollen feet, and shortness of breath. Antenatal appointments become more frequent as you approach your due date.