Calculator of Baby Due Date

Pregnancy duration is typically 40 weeks (280 days) from the first day of the last menstrual period (LMP) to the due date. However, many factors can affect this timeline. Our calculator helps you estimate your baby's due date based on your last menstrual period or ultrasound date.

How to Use This Calculator

To calculate your estimated due date:

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

The calculator will display your due date and provide additional information about your pregnancy timeline.

How the Due Date is Calculated

The standard pregnancy duration is 40 weeks (280 days) from the first day of the last menstrual period (LMP). The due date is calculated by adding 280 days to the LMP date.

Formula

Due Date = LMP Date + 280 days

For ultrasound dates, the calculation is more complex as it accounts for the exact gestational age at the time of the scan.

In some cases, the due date may be adjusted based on the baby's development observed during an ultrasound.

Factors Affecting Pregnancy Duration

Several factors can influence the length of a pregnancy:

Genetics: Some babies are born earlier or later than the average due date
Complications: Certain medical conditions can affect pregnancy duration
Ultrasound adjustments: If an ultrasound shows the baby is developing faster or slower than expected, the due date may be adjusted
Multiple pregnancies: Twins or other multiples may have different due dates

Note: The calculator provides an estimate. Always consult with your healthcare provider for personalized medical advice.

Worked Example

If your last menstrual period was on January 1, 2023, your estimated due date would be:

Due Date = January 1, 2023 + 280 days = October 8, 2023

This means your baby would be expected to arrive around October 8, 2023, give or take a few weeks.

Frequently Asked Questions

How accurate is the due date calculator?

The calculator provides an estimate based on standard pregnancy duration. Actual due dates can vary, so it's important to consult with your healthcare provider for personalized advice.

Can I use this calculator if I had an ultrasound?

Yes, you can enter your ultrasound date and the calculator will adjust the due date based on the baby's estimated gestational age at the time of the scan.

What if my pregnancy is longer or shorter than 40 weeks?

The calculator uses the standard 40-week duration. If your pregnancy is longer or shorter, your healthcare provider may adjust the due date based on ultrasound findings.

Is the due date the same as the expected delivery date?

Yes, the due date is typically the same as the expected delivery date, though deliveries can occur up to 2 weeks before or after this date.