Baby Due Date Calculator Baby Center

Calculating your baby's due date is an important part of tracking your pregnancy. Our Baby Due Date Calculator provides accurate estimates based on your last menstrual period (LMP) or ultrasound date. This tool helps you plan for your baby's arrival and understand your pregnancy timeline.

How to Use This Calculator

Using our Baby Due Date Calculator is simple. Follow these steps:

Select whether you want to calculate based on your last menstrual period (LMP) or ultrasound date.
Enter the relevant date in the provided field.
Click the "Calculate" button to see your estimated due date.
Review the result and any additional information provided.

The calculator will provide your estimated due date based on standard pregnancy lengths. Keep in mind that due dates are estimates and actual delivery dates can vary.

How the Due Date Calculation Works

The standard pregnancy length is considered to be 40 weeks (280 days) from the first day of your last menstrual period (LMP). This is based on the average length of human pregnancies.

Formula

Estimated Due Date = Last Menstrual Period + 280 days (40 weeks)

For ultrasound dates, the calculation is based on the gestational age at the time of the ultrasound plus the remaining weeks of pregnancy.

For example, if your last menstrual period was on January 1, 2023, your estimated due date would be October 31, 2023 (280 days later).

Important Notes About Due Dates

It's important to remember that due dates are estimates, not guarantees. Many factors can affect when you deliver, including:

Your individual pregnancy length
Your previous pregnancies
Your health and medical history
Your baby's position and development

Due dates are typically calculated based on the first day of your last menstrual period. However, some calculators use the first day of your last menstrual period plus 3 days, which can result in a slightly different due date.

Your healthcare provider will monitor your pregnancy closely and may adjust your due date based on ultrasound measurements and other factors.

Common Questions About Due Dates

How accurate are due date calculations?: Due date calculations are estimates based on average pregnancy lengths. Actual delivery dates can vary, so it's important to work closely with your healthcare provider throughout your pregnancy.
Can my due date change during pregnancy?: Yes, your due date can change based on ultrasound measurements and other factors. Your healthcare provider will monitor your pregnancy and may adjust your due date as needed.
What if I don't know my last menstrual period?: If you don't know your last menstrual period, you can use an ultrasound date to estimate your due date. The calculator will ask for your gestational age at the time of the ultrasound.
When should I start preparing for my baby's arrival?: It's a good idea to start preparing for your baby's arrival as soon as you know you're pregnant. This includes making a birth plan, setting up your nursery, and preparing for the changes that come with parenthood.