Pregnancy Calculator Baby Center

This pregnancy calculator helps you determine your due date, gestational age, and track your baby's development. Simply enter your last menstrual period date or ultrasound date to get accurate estimates.

How to Use This Calculator

Using our pregnancy calculator is simple. You have two options to calculate your due date:

Enter the first day of your last menstrual period (LMP)
Enter the date of your ultrasound and the gestational age at that time

The calculator will then provide you with:

Your estimated due date
Current gestational age
Baby's development stage
Trimester information

For the most accurate results, use the date of your first missed period rather than the last normal period. If you had an ultrasound, this method provides the most precise due date.

Formula Used

The standard formula for calculating a pregnancy due date is:

Due Date = Last Menstrual Period + 280 days

Gestational Age = Current Date - Last Menstrual Period

For calculations based on ultrasound:

Due Date = Ultrasound Date + (280 days - Gestational Age at Ultrasound)

The calculator uses these formulas to provide accurate estimates based on your input.

Interpreting Results

Understanding your pregnancy timeline is important for tracking your baby's growth. Here's what each result means:

Gestational Age	Trimester	Baby Development
0-12 weeks	First Trimester	Organ formation, heart begins to beat
13-27 weeks	Second Trimester	Rapid growth, fingers and toes form
28-40 weeks	Third Trimester	Preparation for birth, fat stores accumulate

Your due date is calculated as 40 weeks from your last menstrual period or the date of conception. However, due dates can vary by about 2 weeks either side of the estimated date.

Worked Example

Let's look at an example to see how the calculator works. Suppose:

Your last menstrual period started on January 1, 2023
Today is April 1, 2023

Using the calculator:

Enter January 1, 2023 as your last menstrual period date
Select "Last Menstrual Period" as your calculation method
Click "Calculate"

The calculator will show:

Due Date: October 28, 2023
Gestational Age: 10 weeks
Baby's development: Organ formation, heart begins to beat
Trimester: First Trimester

Remember, this is an estimate. Your actual due date may vary by a week or two either side of the calculated date.

Frequently Asked Questions

How accurate is the pregnancy calculator?

The calculator provides an estimate based on standard pregnancy timelines. For the most accurate information, consult with your healthcare provider, especially if you had an ultrasound.

Can I use this calculator if I'm pregnant with twins or multiples?

This calculator is designed for single pregnancies. Multiple pregnancies have different timelines and should be monitored by a healthcare professional.

What if I had an ultrasound? How do I use that information?

Select the "Ultrasound Date" option and enter both the date of your ultrasound and the gestational age at that time. The calculator will adjust the due date accordingly.

Why does my due date vary from what my doctor said?

Due dates can vary by about 2 weeks either side of the estimated date. Factors like ovulation timing, fertility treatments, and medical interventions can affect the final date.