Trimester Calculator
See the exact date range for each trimester, which one you're in now, and what to expect.
About this calculator
Enter your last menstrual period to see the calculated date range for all three trimesters, which one is currently active, how many days remain in it, and a brief summary of what's generally expected during that stage. Trimester boundaries here follow the standard convention used in prenatal care (first trimester through 13 weeks 6 days, second through 27 weeks 6 days, third from 28 weeks onward).
In broad strokes, the first trimester is when the major organs and body structures form, and it's when many people experience nausea and fatigue. The second trimester is often described as the most comfortable stretch: nausea commonly eases, and many people first feel movement between about 16 and 25 weeks. A detailed anatomy ultrasound is usually done around 18 to 22 weeks. The third trimester is focused on growth and preparation for birth, with prenatal appointments typically becoming more frequent.
Screening and testing schedules vary by provider, country, and individual circumstances, so the timing of any particular test is best confirmed with your own care team. The guides section has a fuller description of each trimester.
Frequently asked questions
- Do all providers use the same trimester boundaries?
- The boundaries used here (13w6d and 27w6d) are the standard convention, but you may occasionally see slightly different week cutoffs used informally. The differences are minor and don't affect the overall picture of your pregnancy's progress.
- Is what happens in each trimester the same for everyone?
- No, the summaries here describe general, commonly-reported experiences. Every pregnancy is different, and this isn't a substitute for guidance from your own healthcare provider.
- How many weeks is each trimester?
- Using the standard boundaries, the first trimester runs from week 1 through 13 weeks 6 days, the second from 14 weeks through 27 weeks 6 days, and the third from 28 weeks until birth, typically around 40 weeks.