How many weeks pregnant?

Calculate from LMP, ultrasound, or IVF

Dating Method

First Day of Last Menstrual Period The first day of bleeding, not the last

Ultrasound Date

Weeks at Ultrasound

Days

Embryo Transfer Date

Embryo Type

Gestational Age

Fetal Age

Due Date

Days Remaining

Trimester

ACOG Classification

Here’s what your result means

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Medical Disclaimer: This tool provides general educational estimates. Always consult your prescribing physician or healthcare provider before making medication changes or interpreting results from population-based models.

Frequently Asked Questions

From first day of last menstrual period (LMP). Includes ~2 weeks before conception. Due date = LMP + 280 days.

Fetal age = gestational age minus 14 days. Gestational age is the standard used in obstetrics.

Only 5% of babies born on due date. First-trimester ultrasound accurate within 5-7 days.

Early term: 37-38 weeks. Full term: 39-40 weeks. Late term: 41 weeks. Post-term: 42+ weeks.

Sources

ACOG Committee Opinion No. 700. 2017. Link
ACOG Definition of Term Pregnancy. 2013. Link

Methodology

Days since LMP-equivalent date. For ultrasound: back-calculated from reported age. For IVF: LMP = transfer date - (14 + embryo days). Due date: LMP + 280 days.

Gestational age counts from LMP. Full term: 39-40 weeks. Due date = LMP + 280 days. Only 5% of babies arrive on due date.

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Trimester milestones Due date accuracy Baby development Prenatal testing