Health
Due date
A 280-day estimate from the last menstrual period.
Result
Enter the first day of the last period. The due date is 280 days later.
How this works
The due date is 280 days after the first day of the last menstrual period, which is 40 weeks. A conception estimate, for this page only, is 14 days after that same start. The first trimester is shown through 13 weeks, and the second through 27 weeks. Those cutovers are a simple teaching split, not a clinical ruling.
Weeks pregnant are the days between the period start and the “count from” date, grouped into weeks and leftover days.
An example
A last period starting January 1, 2026, gives a due date of October 8, 2026. Counted from April 1, 2026, that is 12 weeks and 6 days.