My Baby Due Date Calculator

Pregnancy due dates are calculated based on the first day of your last menstrual period (LMP) or your ultrasound date. This calculator provides an estimated due date using standard gestational periods.

How to Use This Calculator

To calculate your baby's 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 ultrasound date
Click "Calculate" to see your estimated due date

The calculator uses standard gestational periods of 40 weeks (280 days) from the first day of your last menstrual period or from your ultrasound date.

Formula Used

When using last menstrual period (LMP):

Due Date = LMP Date + 280 days (40 weeks)

When using ultrasound date:

Due Date = Ultrasound Date + (280 days - weeks since ultrasound × 7 days)

This formula accounts for the standard gestational period of 40 weeks (280 days) from the first day of your last menstrual period or from your ultrasound date.

Worked Example

If your last menstrual period started on January 1, 2023:

LMP Date: January 1, 2023
Adding 280 days: October 28, 2023
Estimated Due Date: October 28, 2023

If you had an ultrasound on March 15, 2023, and it showed your baby was 12 weeks old:

Ultrasound Date: March 15, 2023
Weeks since ultrasound: 12 weeks
Days to add: 280 - (12 × 7) = 280 - 84 = 196 days
Adding 196 days to March 15, 2023: October 1, 2023
Estimated Due Date: October 1, 2023

Interpreting Your Results

The estimated due date provided by this calculator is based on standard gestational periods. Keep in mind that:

Every pregnancy is unique, and due dates can vary
This calculator provides an estimate, not an exact prediction
Your healthcare provider will monitor your pregnancy and may adjust the due date as needed

Note: The average length of pregnancy is 40 weeks (280 days) from the first day of your last menstrual period. However, some pregnancies may be shorter or longer than this average.

Frequently Asked Questions

How accurate is the due date calculator?

The calculator provides an estimate based on standard gestational periods. For precise due dates, consult with your healthcare provider.

Can I use this calculator if I had an ultrasound?

Yes, you can use the ultrasound date option to calculate a more accurate due date based on your baby's gestational age.

What if my due date changes during pregnancy?

Due dates can change based on your healthcare provider's observations. Regular prenatal visits help monitor your pregnancy and adjust the due date as needed.

Is the due date the same as the delivery date?

No, the due date is an estimate. Actual delivery may occur before or after the due date, especially if you go into labor early or need induction.