Health & Fitness
Pregnancy Week Calculator
Calculate current pregnancy week, trimester, and due date.
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
How are pregnancy weeks counted?
From the first day of your last menstrual period, even though conception occurs ~2 weeks later.
Why adjust for cycle length?
Standard calculation assumes 28-day cycle. Longer/shorter cycles shift ovulation timing.
When does each trimester start?
First: weeks 1-12, Second: weeks 13-26, Third: weeks 27-40.
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About this tool
This Pregnancy Week Calculator turns your inputs into practical results. Provide Last Menstrual Period, Cycle Length, and week to calculate Current Week and Trimester.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.