Calculator

OB-Gyn — EDD & Gestational Age

Estimate Expected Date of Delivery (Naegele's rule) and current Gestational Age from the patient's last menstrual period (LMP).

EDD = LMP + 7 days − 3 months + 1 year · GA = today − LMP

Last Menstrual Period (LMP)

First day of the last normal menstrual period.

Today

Defaults to today. Backdate to cross-check earlier ANC records.

Naegele's rule assumes a regular 28-day cycle. For irregular cycles or after IVF, prefer ultrasound dating in the first trimester (CRL).

Gestational Age

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Estimated Date of Delivery

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Trimester

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Days remaining

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Select an LMP date.

Section

Estimated Fetal Weight (Johnson-Toshack)

Bedside fetal weight estimate from fundal height and station of the presenting part.

Fundal height (TFU)

Station of presenting part

Formula assumes vertex presentation. Less reliable in polyhydramnios, oligohydramnios, multiple gestation, or BMI >30.

Estimated fetal weight

—g

Enter fundal height to estimate fetal weight.