EDD Calculator - Estimated Date of Delivery

How Your Due Date Is Calculated

An estimated date of delivery (EDD) is calculated using a standard 280-day (40-week) pregnancy timeline. The most common method relies on the first day of your last menstrual period (LMP). By adding 280 days to the LMP date, the calculator provides a due date estimate. If you know your conception date instead, the calculator adds 266 days, as conception typically occurs around day 14 of a standard 28-day cycle.

This method assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. For individuals with longer or shorter cycles, or irregular periods, the estimate may be less precise. In clinical settings, an early ultrasound is often used to adjust the due date for greater accuracy.

How to Use the EDD Calculator

1. Select your preferred input method: Last Menstrual Period (LMP) or Conception Date.
2. Enter the date in the provided field.
3. Click or tap the calculate button to see your estimated due date.

The calculator instantly displays the estimated delivery date based on the standard 40-week pregnancy duration. No additional inputs are required.

Understanding Your Results

The estimated date of delivery is exactly that — an estimate. Only about 5% of babies are born on their exact due date. A full-term pregnancy is considered anywhere from 37 weeks to 42 weeks. Your result should be used as a general reference point for planning and prenatal care discussions with your healthcare provider.

The calculator does not account for individual variations such as cycle irregularity, multiple pregnancies (twins, triplets), or medical conditions that may affect gestational length. Always confirm your due date with a medical professional.

Common Questions About Due Dates

Why is the LMP method used instead of conception date?

Many people do not know their exact conception date. The first day of the last menstrual period is easier to recall and provides a consistent starting point for pregnancy dating. The 280-day rule is a medical standard that has been used for decades.

Can my due date change?

Yes. Healthcare providers may adjust your due date based on early ultrasound measurements, especially if there is a significant discrepancy between the LMP-based estimate and fetal size measurements in the first trimester.

What if my cycle is longer or shorter than 28 days?

The standard calculation assumes a 28-day cycle. If your cycle is consistently longer or shorter, ovulation and conception likely occurred on a different day. An ultrasound is the most reliable way to date a pregnancy in these cases.