How is the week calculated?

From the first day of the last menstrual period (LMP) to the chosen date.

How accurate is the due date?

It uses Naegele's rule (LMP + 280 days); an ultrasound is more precise.

No — consult your doctor for clinical dates.

Find current pregnancy week, trimester and estimated due date from the last menstrual period. Runs in your browser.

Last period (LMP)

As of date