How is due date calculated?

Naegele’s rule adds 280 days (40 weeks) to the first day of the last menstrual period for a typical 28-day cycle.

Is this medical advice?

No. This is an educational estimate. Confirm dates with a qualified clinician.

What if my cycle isn’t 28 days?

Adjust the cycle length field. Longer cycles often push the estimate later; shorter earlier.

Due Date Calculator — Pregnancy Due Date Free

First day of last menstrual period (LMP)

Average cycle length (days)

Estimate

Due date

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Educational estimate only — not medical advice. Only a clinician can confirm dating (ultrasound, exams). Seek professional care for pregnancy questions.

How this due date calculator works

Enter the first day of your last menstrual period.
Set your typical cycle length (default 28).
Read estimated due date, current week, and trimester.

FAQ

How accurate is Naegele’s rule?

It is a common starting estimate. Actual delivery dates vary; many births are within two weeks of the estimated due date.

Due Date Calculator

Estimate

How this due date calculator works

FAQ

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