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Home / Calculators / Due Date Calculator

Free Pregnancy Due Date Calculator

Calculate your estimated due date (EDD) and current gestational age based on your last menstrual period or conception date.

Method:
First day of your last period
Date of conception (if known)
days (average is 28 days)
Used to calculate current gestational age
Please enter a valid date.
Your Estimated Due Date (EDD)
—
Based on a 28-day cycle using Naegele's rule
Current Pregnancy Status
0
Weeks Pregnant
0
Days
1st
Trimester
Key Milestones
—
Estimated Conception
0
Weeks Remaining
0
Days Until Due Date
0%
Pregnancy Complete
Trimester Milestones
Key developmental milestones throughout your pregnancy journey.
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How to Use the Due Date Calculator

1

Choose Your Method

Select either LMP Date or Conception Date as your calculation method. LMP is the most common method used by healthcare providers.

2

Enter Your Dates

Enter your LMP or conception date, your typical cycle length (default 28 days), and confirm today's date.

3

Get Your Results

View your estimated due date, current gestational age, trimester, weeks remaining, and key pregnancy milestones.

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Understanding Your Due Date

Your estimated due date (EDD) is calculated using Naegele's rule, the standard formula used by obstetricians and midwives worldwide. The rule adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day menstrual cycle with conception occurring on day 14.

It is important to understand that the due date is an estimate — only about 4% of babies are born exactly on their due date. A full-term pregnancy is considered anywhere between 37 weeks and 42 weeks. Your healthcare provider may adjust your due date based on early ultrasound measurements, especially if your cycles are irregular or if the ultrasound measurements differ significantly from your LMP-based dates.

The three trimesters of pregnancy each bring distinct developmental milestones:

Trimester Weeks Key Developments
First Trimester Weeks 1–13 Major organs and systems develop; heart begins beating; morning sickness common
Second Trimester Weeks 14–27 Baby grows rapidly; movements felt; gender can be determined; energy often improves
Third Trimester Weeks 28–40+ Rapid brain and lung development; baby gains weight; preparations for birth

Frequently Asked Questions

Your due date is calculated using Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is the standard method healthcare providers use. If you know your conception date, you can also calculate by adding 266 days (38 weeks) to that date. Our calculator supports both methods and adjusts for your specific cycle length.

Naegele's rule is the standard formula used to calculate a pregnancy's estimated due date. It works by taking the first day of your last menstrual period (LMP), adding 1 year, subtracting 3 months, and adding 7 days. For example, if your LMP was January 1, 2026, your estimated due date would be October 8, 2026. This method assumes a 28-day menstrual cycle and conception occurring on day 14.

The due date calculator provides an estimated due date (EDD), but only about 4% of babies are born exactly on their due date. Most pregnancies last between 37 and 42 weeks. The calculator is most accurate when you have regular 28-day cycles and know the exact first day of your LMP. Your healthcare provider may adjust your due date based on early ultrasound measurements, which are most accurate when performed between weeks 8 and 13.

If you have irregular periods or a cycle length different from 28 days, you can adjust the cycle length in our calculator. For longer cycles, ovulation and conception occur later, which shifts the due date forward. For shorter cycles, the due date shifts backward. Our calculator accounts for your specific cycle length to provide a more personalized estimate. However, an early ultrasound is the most reliable way to date a pregnancy if your cycles are irregular.

Gestational age is the number of weeks and days since the first day of your last menstrual period (LMP). It is the standard way healthcare providers track pregnancy progress. A full-term pregnancy is typically 40 weeks (280 days) gestational age. This differs from fetal age (also called conceptional age), which is about 2 weeks less since it dates from conception. Our calculator shows both your weeks pregnant and estimated conception date.

Yes, it is completely free. There are no hidden charges, subscription plans, or usage limits. You can use it as many times as you like, for any purpose — personal, educational, or professional. No registration or sign-up is required.

No, absolutely not. Your dates and results are processed entirely on your device using client-side JavaScript. No data is sent to any server, stored in cookies, or tracked in any way. Your privacy is fully protected — this is a core principle of FreeNestTools.

Pregnancy is divided into three trimesters:
  • First Trimester (weeks 1–13): Major organ development, heart begins beating, morning sickness common
  • Second Trimester (weeks 14–27): Baby grows rapidly, movements felt, gender can be determined
  • Third Trimester (weeks 28–40+): Rapid brain and lung development, baby gains weight, preparations for birth
Each trimester has distinct developmental milestones and changing care needs. Always consult your healthcare provider for personalized guidance.

Yes. Our calculator supports both methods. If you know the exact date of conception (when the egg was fertilized), select the Conception Date method. The calculator will add approximately 266 days (38 weeks) to the conception date to estimate your due date. This method can be useful if you conceived through fertility treatments or tracked ovulation closely. The conception-based calculation is generally more accurate for those who know their exact ovulation date.

Absolutely. The tool is fully responsive and works on all devices — desktops, laptops, tablets, and smartphones. The layout adapts to your screen size for a comfortable experience on any device.
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