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Pregnancy Due Date Calculator

Last Menstrual Period Conception Date Due Date

First day of last menstrual period

Conception date (if known)

Estimated due date

About the Pregnancy Due Date Calculator

This due date calculator estimates your expected delivery date and current gestational age based on your last menstrual period, conception date, or known due date. Pregnancy typically lasts about 40 weeks (280 days) from the first day of your LMP.

The Formula

Estimated Due Date = LMP + 280 days (40 weeks). Gestational age = current date minus LMP, expressed in weeks and days. Conception typically occurs about 14 days after LMP, so due date can also be estimated as conception date + 266 days.

Frequently Asked Questions

How accurate is the due date?

Only about 4% of babies are born on their exact due date. Full-term pregnancy ranges from 37 to 42 weeks. The due date is an estimate and your healthcare provider may adjust it based on early ultrasound measurements.

What is the difference between gestational age and fetal age?

Gestational age is measured from the first day of your LMP (about 40 weeks total). Fetal age (conception age) is measured from conception and is typically 2 weeks less than gestational age. Healthcare providers use gestational age for tracking pregnancy progress.