Estimated Due Date Calculator
Use this calculator to estimate your baby's due date based on your current pregnancy week or your last menstrual period (LMP).
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function calculateEDD() {
var currentWeeksPregnantInput = document.getElementById('currentWeeksPregnant').value;
var currentDaysPregnantInput = document.getElementById('currentDaysPregnant').value;
var lastMenstrualPeriodDateInput = document.getElementById('lastMenstrualPeriodDate').value;
var eddResultDiv = document.getElementById('eddResult');
var weeksRemainingResultDiv = document.getElementById('weeksRemainingResult');
var trimesterResultDiv = document.getElementById('trimesterResult');
var lmpEddResultDiv = document.getElementById('lmpEddResult');
var errorMessageDiv = document.getElementById('errorMessage');
eddResultDiv.innerHTML = ";
weeksRemainingResultDiv.innerHTML = ";
trimesterResultDiv.innerHTML = ";
lmpEddResultDiv.innerHTML = ";
errorMessageDiv.innerHTML = ";
var today = new Date();
today.setHours(0, 0, 0, 0); // Normalize today's date to start of day
var isValidInput = false;
// — Method 1: Calculate based on Current Weeks Pregnant —
var currentWeeks = parseInt(currentWeeksPregnantInput);
var currentDays = parseInt(currentDaysPregnantInput);
if (!isNaN(currentWeeks) && currentWeeks >= 1 && currentWeeks <= 40) {
if (isNaN(currentDays) || currentDays 6) {
currentDays = 0; // Default to 0 if invalid or not provided
}
isValidInput = true;
var totalDaysPregnantSoFar = (currentWeeks * 7) + currentDays;
var daysRemainingUntilFullTerm = 280 – totalDaysPregnantSoFar;
if (daysRemainingUntilFullTerm < 0) {
errorMessageDiv.innerHTML = 'You are past 40 weeks. Please consult your doctor.';
return;
}
var eddDate = new Date(today.getTime() + (daysRemainingUntilFullTerm * 24 * 60 * 60 * 1000));
var weeksRemaining = Math.floor(daysRemainingUntilFullTerm / 7);
var daysRemainder = daysRemainingUntilFullTerm % 7;
eddResultDiv.innerHTML = '
Based on current weeks: ' + eddDate.toLocaleDateString('en-US', { year: 'numeric', month: 'long', day: 'numeric' });
weeksRemainingResultDiv.innerHTML = 'Approximately ' + weeksRemaining + ' weeks and ' + daysRemainder + ' days remaining until your due date.';
var currentTrimester = ";
if (currentWeeks >= 1 && currentWeeks = 14 && currentWeeks = 28 && currentWeeks <= 40) {
currentTrimester = 'Third Trimester';
}
trimesterResultDiv.innerHTML = 'You are currently in your ' + currentTrimester + '.';
}
// — Method 2: Calculate based on Last Menstrual Period (LMP) —
if (lastMenstrualPeriodDateInput) {
var lmpDate = new Date(lastMenstrualPeriodDateInput + 'T00:00:00'); // Ensure UTC for consistent date parsing
if (!isNaN(lmpDate.getTime())) {
isValidInput = true;
var eddDateLMP = new Date(lmpDate.getTime() + (280 * 24 * 60 * 60 * 1000));
lmpEddResultDiv.innerHTML = '
Based on LMP: ' + eddDateLMP.toLocaleDateString('en-US', { year: 'numeric', month: 'long', day: 'numeric' });
// If only LMP is provided, calculate current weeks and trimester from LMP
if (!currentWeeksPregnantInput) {
var diffTime = Math.abs(today.getTime() – lmpDate.getTime());
var currentWeeksFromLMP = Math.floor(diffTime / (1000 * 60 * 60 * 24 * 7));
var currentTrimesterLMP = ";
if (currentWeeksFromLMP >= 1 && currentWeeksFromLMP = 14 && currentWeeksFromLMP = 28 && currentWeeksFromLMP <= 40) {
currentTrimesterLMP = 'Third Trimester';
}
if (currentTrimesterLMP) {
trimesterResultDiv.innerHTML = 'Based on LMP, you are approximately ' + currentWeeksFromLMP + ' weeks pregnant, in your ' + currentTrimesterLMP + '.';
}
}
}
}
if (!isValidInput) {
errorMessageDiv.innerHTML = 'Please enter valid "Current Weeks Pregnant" (1-40) OR a "Last Menstrual Period Date".';
}
}
Understanding Your Estimated Due Date (EDD)
The Estimated Due Date (EDD), also known as the Estimated Date of Confinement (EDC), is a crucial milestone in pregnancy. It's the date when your baby is expected to be born. While only a small percentage of babies are born exactly on their due date (around 4-5%), it provides a valuable timeline for monitoring your pregnancy and preparing for your baby's arrival.
How is the EDD Calculated?
Traditionally, an EDD is calculated by adding 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). This method assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. However, not all women have regular cycles, and the exact date of conception can vary.
Our EDD calculator offers two primary methods to help you determine your due date:
-
Based on Current Weeks Pregnant: If you've recently had an ultrasound or a doctor's visit that confirmed your current gestational age in weeks and days, this method provides a precise estimate. The calculator takes your current pregnancy duration and projects forward to the typical 40-week full-term mark from the LMP.
Example: If you are currently 12 weeks and 3 days pregnant, the calculator will determine how many days are left until 280 days (40 weeks) and add that duration to today's date to give you your EDD.
-
Based on Last Menstrual Period (LMP): If you know the exact date of your last menstrual period, this is a straightforward way to calculate your EDD. The calculator simply adds 280 days (40 weeks) to your LMP date.
Example: If your LMP was January 1, 2024, your EDD would be around October 8, 2024 (January 1 + 280 days).
The Trimesters of Pregnancy
Pregnancy is typically divided into three trimesters, each with its own unique developmental milestones for the baby and changes for the mother:
-
First Trimester (Weeks 1-13): This period begins with conception and is marked by rapid cell division and the formation of major organs. Many women experience morning sickness and fatigue.
Example: If you are 8 weeks pregnant, you are in your first trimester.
-
Second Trimester (Weeks 14-27): Often considered the "golden trimester," many women find their energy returns and morning sickness subsides. The baby grows significantly, and you might start to feel movements.
Example: If you are 20 weeks pregnant, you are in your second trimester.
-
Third Trimester (Weeks 28-40+): The final stretch! The baby continues to grow and mature, gaining weight and preparing for birth. You might experience more discomfort as your body prepares for labor.
Example: If you are 32 weeks pregnant, you are in your third trimester.
Important Considerations
- Variability: Remember that your EDD is an estimate. Full-term pregnancies can range from 37 to 42 weeks.
- Ultrasound Dating: Early ultrasounds (especially in the first trimester) are often considered the most accurate method for dating a pregnancy, as they measure the baby's size to determine gestational age.
- Consult Your Doctor: Always discuss your EDD with your healthcare provider. They will use various factors, including your LMP, ultrasound findings, and medical history, to provide the most accurate due date for you.
This calculator is a helpful tool for general estimation, but it should not replace professional medical advice.