Pregnancy Due Date Calculator Baby Center

Pregnancy due dates are calculated based on the first day of your last menstrual period (LMP) or the date of a confirmed ultrasound. This calculator helps you estimate your due date using standard medical guidelines.

How to Use This Calculator

To calculate your pregnancy due date:

Select whether you want to use your last menstrual period (LMP) or an ultrasound date.
Enter the relevant date (LMP or ultrasound date).
Click "Calculate" to see your estimated due date.

The calculator uses standard medical guidelines where a full-term pregnancy is considered 40 weeks (280 days) from conception. The due date is typically calculated as 40 weeks after the first day of your last menstrual period.

How Pregnancy Due Dates Are Calculated

The standard method for calculating a pregnancy due date is to add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is based on the average length of a full-term pregnancy.

Formula

Due Date = LMP Date + 280 days

For example, if your LMP was January 1, 2023, your due date would be October 9, 2023.

Ultrasound dates can provide more precise due date calculations. The calculator can use either method based on your preference.

Example Calculation

Let's say you had your last menstrual period on March 15, 2023. Using the standard 40-week calculation:

March 15, 2023 (LMP)
Add 280 days: March 15 + 280 days = December 12, 2023

Therefore, your estimated due date would be December 12, 2023.

This example shows how the calculator works in practice. The actual due date may vary based on individual factors and medical assessments.

Frequently Asked Questions

How accurate is the pregnancy due date calculator?: The calculator provides an estimate based on standard medical guidelines. Actual due dates may vary based on individual factors and medical assessments.
Can I use an ultrasound date instead of my last menstrual period?: Yes, the calculator can use either your last menstrual period or an ultrasound date to calculate your due date.
What if my pregnancy is early or late?: The calculator uses the standard 40-week average. Early or late pregnancies may require medical evaluation.
Is the due date the same as the expected delivery date?: Yes, the due date is typically the expected delivery date, though actual delivery may occur a few days earlier or later.