Due Date Calculator

Category: Pregnancy
- April 03, 2025
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Calculate your estimated due date based on your last menstrual period, conception date, or ultrasound information. This calculator provides an approximate due date and important pregnancy milestones.

Calculation Method

Advanced Options

About Due Date Calculations

The average pregnancy lasts about 40 weeks (280 days) from the first day of the last menstrual period (LMP). Due dates are just estimates – only about 5% of babies are born on their exact due date.

Calculation Methods
  • Last Menstrual Period (LMP): The most common method. Adds 280 days (40 weeks) to the first day of your last period.
  • Conception Date: Adds 266 days (38 weeks) to the date of conception, which is typically about 14 days after the start of the last period.
  • Ultrasound Dating: Uses measurements taken during an ultrasound to determine gestational age, then calculates the due date.
Trimesters

Pregnancy is divided into three trimesters, each lasting about 13-14 weeks:

  • First Trimester: Weeks 1-13 (development of major organs and systems)
  • Second Trimester: Weeks 14-26 (rapid growth and movement)
  • Third Trimester: Weeks 27-40 (final development and preparation for birth)
Terms to Know
  • Gestational Age: Time measured from the first day of the last menstrual period (LMP)
  • Embryonic Age/Fetal Age: Time measured from conception (typically 2 weeks less than gestational age)
  • Full-term: Between 39 weeks, 0 days and 40 weeks, 6 days
  • Early-term: Between 37 weeks, 0 days and 38 weeks, 6 days
  • Late-term: Between 41 weeks, 0 days and 41 weeks, 6 days
  • Post-term: 42 weeks, 0 days and beyond

Formula Used for Due Date Calculation

From Last Menstrual Period (LMP):
Due Date = First Day of LMP + 280 days (40 weeks)

From Conception Date:
Due Date = Conception Date + 266 days (38 weeks)

From Ultrasound Data:
Due Date = Ultrasound Date - Gestational Age (in days) + 280 days

What Is the Due Date Calculator?

The Due Date Calculator is a simple, interactive tool to help you estimate when your baby might be born. Whether you're tracking your menstrual cycle, trying to conceive, or already pregnant, this calculator offers a quick way to calculate your Pregnancy due date and understand your pregnancy timeline.

How It Works

You can choose from three methods to estimate your due date:

  • Last Menstrual Period (LMP): The most common method. Adds 280 days to the first day of your last period.
  • Conception Date: Adds 266 days to the date you believe conception occurred.
  • Ultrasound Data: Uses measurements from your scan to estimate gestational age and calculate the due date.

How to Use the Calculator

Follow these simple steps:

  • Select a calculation method: LMP, Conception Date, or Ultrasound.
  • Enter the required date(s) depending on your chosen method.
  • Adjust options like cycle length or gestational age if needed.
  • Click the “Calculate Due Date” button to view your results.

You'll receive your estimated due date, current gestational age, trimester transitions, and a visual pregnancy calendar if selected.

Why Use This Tool?

This due date estimator is especially helpful for:

  • Newly pregnant individuals wanting to estimate baby’s arrival.
  • People trying to conceive who are using a pregnancy planning resource or conception date tool.
  • Users tracking cycles with a Period Calculator or ovulation tracker.

It's also a great addition to your existing tools like a pregnancy week calculator, fertile window tool, or pregnancy weight tracker.

Frequently Asked Questions (FAQ)

Is the due date 100% accurate?

No. It’s an estimate. Only about 5% of babies are born on their exact due date.

Can I use this calculator before I’m pregnant?

Yes. It’s helpful as a fertility window estimator or to plan ahead using your cycle data.

How does cycle length affect the due date?

If your cycle is longer or shorter than 28 days, it shifts your estimated ovulation date and due date accordingly.

What if I had an ultrasound?

Early ultrasounds can provide an accurate gestational age, which the calculator uses to estimate the due date.

What are the benefits of showing the pregnancy calendar?

It helps you visualize your pregnancy timeline, understand trimester transitions, and track milestones like the baby's first heartbeat and viability.

Additional Benefits

  • Includes trimester breakdowns to track pregnancy stages.
  • Displays a milestone table with important pregnancy events.
  • Option to see lunar months for alternative pregnancy tracking.
  • Great companion to tools that track ovulation or predict menstrual dates.

In Summary

This Due Date Calculator helps you estimate your baby’s arrival based on reliable, medically recognized methods. Whether you're looking to track pregnancy gain, estimate your fertile days, or plan your prenatal appointments, this tool offers clear answers at any stage of your journey.