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Gestational age and EDD calculator

Calculate estimated gestational age and EDD by LMP, with clear limits: does not replace obstetric evaluation or early ultrasound.

Calculator

How to interpret

This calculator uses the last menstrual period to estimate the gestational age on the reference date and the estimated EDD. The result is an initial calculation, useful for conversation and organization, but does not replace obstetric evaluation.

Frequently asked questions

Public support sources

The sources below support the general logic of LMP, 40 weeks/280 days, EDD uncertainty, and the importance of early ultrasound when indicated.

• ACOG/SMFM: Methods for Estimating the Due Date
• Johns Hopkins Medicine: Calculating a Due Date
• NHS: Due date calculator
• Merck Manual: Physiology of Pregnancy
• Merck Manual: Gestational Age
• Public ultrasound hub
• Ultrasound preparation
• Editorial policy

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