Pregnancy due date calculator

Estimate due date from last menstrual period or conception date.

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Tool guide

Pregnancy due date calculator: how it works

Practical information to understand the result and use this tool correctly.

About Pregnancy due date calculator

Naegele’s rule approximates the estimated due date (EDD) as about 280 days after the first day of the last menstrual period (LMP).

Ultrasound dating can revise the EDD. Cycle length, ovulation timing, and medical history all affect accuracy.

This is a calendar helper only—not prenatal care. Confirm dates with a qualified clinician.

How to use it

1Enter the LMP date as YYYY-MM-DD.
2Calculate the estimated due date (+280 days).
3Bring the estimate to your care provider for confirmation.

Frequently asked questions

What if cycles are irregular?: LMP-based dates are less reliable; ultrasound is usually preferred for dating.
Conception date instead?: If you know conception timing, clinicians may date from that event rather than LMP—this tool follows the LMP+280 convention.