Estimate pregnancy weeks and days from the first day of the last menstrual period and review a broad trimester grouping.
Estimate gestational age in weeks and days from the first day of the last menstrual period. Pregnancy Week Calculator reports a calendar-based gestational age estimate and broad trimester grouping. Clinical dating may differ when ultrasound or other information is used. How to use Pregnancy Week Calculator: Enter the first day of the last menstrual period. Review the estimated weeks and days. Use the result as a planning reference and confirm clinical dating with your care team. Common uses: Pregnancy calendar planning Preparing prenatal appointment questions General gestational-age estimation How is gestational age counted? It is conventionally counted from the first day of the last menstrual period. Can the week number be different clinically? Yes. Clinical dating can be adjusted based on additional evidence. Does the calculator diagnose pregnancy? No. It only calculates a date-based gestational-age estimate.