Calculate pregnancy week, trimester, and estimated due date from the last menstrual period.
Version 1.0 · Last Updated: August 6, 2026 · Maintained by ToolLarder
Usually 28 days. Enter a value from 21–35 days.
Results are estimates only and are not medical advice. Uncertain dates or irregular cycles can reduce accuracy; first-trimester ultrasound may date the pregnancy more accurately. Follow your obstetric clinician's guidance.