Table of Contents

Due Date Calculator: Get an Estimated Due Date

First day of your last menstrual period:

Important: This is an estimate based on a standard 280-day calculation from your last period, and actual delivery dates vary widely. Only about 5% of babies are born on their exact estimated due date. Always confirm timing with your healthcare provider, who may adjust this based on ultrasound measurements.

How Due Dates Are Actually Calculated

The standard method, called Naegele’s Rule, adds 280 days, 40 weeks, to the first day of your last menstrual period. This assumes a fairly standard cycle length, which is why healthcare providers often adjust the estimate using early ultrasound measurements, which can be more precise for irregular cycles.

Why Due Dates Are Estimates, Not Predictions

Full-term pregnancy is generally considered to span weeks 37 through 42, a five-week window. A due date is the statistical midpoint of a normal range, not a precise prediction, which is why the majority of births happen within a week or two of the estimated date rather than exactly on it.

Frequently Asked Questions

Why did my doctor give me a different date than a calculator?

Early ultrasound dating, particularly in the first trimester, is often considered more accurate than last-period calculations alone and may adjust your estimated date by several days.

Is it a problem if I go past my due date?

Going a few days to a week past your due date is common and not usually a concern on its own; your provider will monitor accordingly.