Trimester Calculator
First, second, or third? See where you are today and when each chapter of your pregnancy begins and ends.
Find out which trimester you’re in today, plus the exact dates each trimester of your pregnancy begins and ends.
How this works
We use ACOG’s trimester definitions: the second trimester begins at 14 weeks 0 days and the third at 28 weeks 0 days of gestational age, counted from the first day of your last period (or your due date minus 280 days). Source: ACOG Committee Opinion 700 and ACOG patient education.
Sources & method
Due-date and gestational-age math follows ACOG Committee Opinion 700, “Methods for Estimating the Due Date” (Naegele’s rule and ART-based dating). Trimester boundaries follow ACOG patient-education definitions. All results are planning estimates, your prenatal healthcare provider determines your clinical due date.
Ready to meet your baby?
Sonographer-led bonding sessions in Woburn, MA. Calm, gentle, and all about you and your little one.
Book Now