Pregnancy Due Date Calculator

First day of your last menstrual period

Average cycle length (days)

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Estimated Due Date

Current pregnancy week—

End of first trimester—

End of second trimester—

Full term date—

How is the due date calculated?

This calculator uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. If your cycle differs from 28 days, the estimate is adjusted accordingly.

What does the due date mean?

Only about 5% of babies are born on their exact due date. Most arrive within two weeks before or after. The due date is an estimate, not a deadline.

Trimesters explained

Pregnancy is divided into three trimesters. The first runs from weeks 1 to 13, the second from weeks 14 to 26, and the third from weeks 27 to 40.