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Pregnancy Trimesters

Trimester Calculator

Find out which trimester you are in today, from your due date or last period, with the dates each one starts and ends.

How trimesters are divided

Pregnancy is split into three trimesters based on weeks counted from your last menstrual period (LMP). This calculator works from your due date, LMP, or conception date.

  • First trimester: weeks 1–13.
  • Second trimester: weeks 14–27.
  • Third trimester: week 28 to birth (term is 37 weeks).

Enter a date

Your current trimester and key dates will appear here.
You are in the
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Current week
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2nd trimester starts
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3rd trimester starts
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Estimated due date
Note: Trimester boundaries vary slightly between sources. This is an estimate for planning, not medical advice.

What each trimester involves

Each stage has its own focus for checkups and wellbeing:

Related reading

How Many Weeks Pregnant Am I? How to Count Pregnancy WeeksHow Many Months Pregnant Am I? Weeks to Months ExplainedPregnancy Trimesters Explained

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