Gestational age estimate
Turn a last-period date into an estimated gestational age in completed weeks and days. It is a helpful translation—not a replacement for clinical dating.
Your dates stay on this device. Nothing you enter here is saved or sent to Flowy.
The calculation
The calculator counts complete days from the first day of the last menstrual period to today—or to another date you choose. Every seven complete days becomes one gestational week.
It also adds 280 days to the last-period date for a standard due-date estimate and groups the elapsed time into a broad trimester.
Good to know
This count is only as reliable as the date behind it. Irregular cycles, uncertain dates, and ovulation that happened earlier or later than average can all change the estimate.
Use the gestational age and due date confirmed by your maternity team for appointments, screening windows, medication decisions, or concerns about the pregnancy.
Common questions
Gestational age is conventionally counted from the first day of the last menstrual period. In a typical 28-day cycle, that is about two weeks before conception.
It means 8 complete weeks and 3 additional days have passed since the gestational start date used for dating. You are in your ninth week of pregnancy.
This tool labels weeks 0–13 as the first trimester, weeks 14–27 as the second, and week 28 onward as the third. Clinical resources sometimes present boundaries slightly differently.
Do not guess for medical decisions. A healthcare professional can use your history and ultrasound findings to establish the best obstetric estimate.
