Pregnancy Due Date Calculator
Estimate a due date and current gestational week from calendar dates
How the due date is estimated
The starting point is the first day of the last menstrual period. For a 28-day cycle, 280 days are added; the difference in cycle length shifts both due date and estimated conception.
How gestational weeks are counted
Counting begins with the last period, roughly two weeks before conception. A notation such as 12+3 means twelve completed weeks and three additional days.
A due date represents a range
The calculated day is not a precise prediction. Cycle variation and uncertainty about the period date can shift the estimate. Treat the date as orientation and discuss medical questions with a qualified clinician.
Irregular cycles, IVF, and ultrasound
Calendar dating is less reliable with irregular cycles. IVF dates and clinician-led ultrasound dating use different information and are not converted here. A medical dating assessment takes priority.