Calculate Baby Due Date Last Period

Pregnancy lasts approximately 40 weeks from the first day of your last menstrual period. This calculator estimates your due date by adding 40 weeks (280 days) to your last period date. While this is a general guideline, actual due dates can vary.

How to Use This Calculator

To calculate your baby's due date:

Enter the date of your last menstrual period in the calculator below.
Click "Calculate" to see your estimated due date.
Review the result and understand the calculation method.

The calculator will display your due date and show the pregnancy timeline in a chart.

How the Due Date Calculation Works

Pregnancy is typically measured from the first day of your last menstrual period. The standard duration is 40 weeks (280 days), though some pregnancies may be slightly shorter or longer.

Formula

Due Date = Last Period Date + 280 days

This calculation assumes a full-term pregnancy of 40 weeks.

The calculator uses this simple formula to estimate your due date. Keep in mind that:

Pregnancy lengths can vary by a few days
Some medical conditions may affect pregnancy duration
Ultrasound measurements provide more precise due dates

Example Calculation

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

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

This example shows the standard calculation. Your actual due date may vary.

Frequently Asked Questions

Is the due date calculator accurate?

The calculator provides an estimate based on standard pregnancy duration. For precise due dates, consult your healthcare provider or use ultrasound measurements.

Can pregnancy be shorter or longer than 40 weeks?

Yes, some pregnancies are slightly shorter (around 38-39 weeks) or longer (up to 42 weeks). These variations are normal.

When should I see a doctor about my pregnancy?

You should contact your healthcare provider if you miss your period and experience symptoms like nausea, vomiting, or breast tenderness.