Health & Fitness

What Is an Estimated Due Date?

An estimated due date (EDD) is the projected date of childbirth, typically calculated as 280 days (40 weeks) after the first day of the last menstrual period. This method is known as Naegele's rule. Only a small percentage of babies are born on their exact due date.

Naegele's Rule

First day of last period + 1 year − 3 months + 7 days gives the same result as adding 280 days, assuming a 28-day cycle.

Ultrasound Dating

An early ultrasound may be used by healthcare providers to confirm or adjust the estimate.

🧮 Calculate It Yourself

Put Estimated Due Date (EDD) into practice with these free calculators — no sign-up, nothing stored.

👶 Pregnancy Due Date Calculator Estimate your due date based on your last menstrual period. Calculate → 📅 Date Calculator Find days between two dates, or add/subtract days from a date. Calculate →

🔗 Related Terms

Gestational Age Menstrual Cycle Fertile Window

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Last updated: September 27, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.