How this calculator works
Your pregnancy is dated from the first day of your last menstrual period (LMP), and your due date is 280 days (40 weeks) after that. If you enter a due date, we count back 280 days to find that starting point; if you enter your last period, we adjust it for your cycle length first; if you enter a scan result, we use the due date it gave you (or count back from the scan date by how far along it showed you). Then:
- Weeks pregnant = whole weeks between the starting point and today; the leftover days are shown too.
- Trimester: first until 13 weeks 6 days, second from 14 weeks to 27 weeks 6 days, third from 28 weeks.
- Days to go = days between today and your due date.
Don't know your due date yet? Use the due date calculator first. Wondering when your baby was conceived? Try the conception date calculator.
