Calculating how many weeks pregnant you are is a crucial part of monitoring your pregnancy. The standard method uses your Estimated Due Date (EDD) and the current date to determine your gestational age. This calculator helps you quickly and accurately determine this important metric.
How is Gestational Age Calculated?
Gestational age is typically calculated from the first day of your Last Menstrual Period (LMP), not the date of conception. However, when you know your Estimated Due Date (EDD), you can work backward to find your current weeks pregnant.
A full-term pregnancy is considered to be 40 weeks from the first day of the LMP. This is equivalent to 280 days. The calculation performed by this tool is based on the difference between your Estimated Due Date and the current date.
The formula used is:
Step 1: Determine the number of days between the Estimated Due Date (EDD) and Today's Date.
Step 2: Since a pregnancy is considered 40 weeks (280 days) from the LMP, we count backward from the EDD. A pregnancy is typically 40 weeks + 0 days at the EDD.
Step 3: The number of days remaining until the EDD is subtracted from 280 days.
Step 4: This difference in days is then divided by 7 to get the number of weeks and remaining days.
Specifically, the calculation is:
Weeks Pregnant = (280 days - Days Remaining Until EDD) / 7
Where 'Days Remaining Until EDD' is the number of days from the current date to the Estimated Due Date.
Example Calculation
Let's assume:
Estimated Due Date (EDD): October 26, 2024
Today's Date: July 15, 2024
1. Days Remaining Until EDD: From July 15, 2024, to October 26, 2024, there are 103 days remaining.
2. Calculate Total Gestational Days: A pregnancy is considered 40 weeks (280 days) from LMP. At the EDD, you are 40 weeks pregnant. So, we subtract the days remaining from 280.
3. Weeks Pregnant: (280 days – 103 days) / 7 days/week = 177 days / 7 days/week = 25.28 weeks.
This means on July 15, 2024, the individual is approximately 25 weeks pregnant.
Why is this Calculator Useful?
This calculator is invaluable for expecting parents, healthcare providers, and anyone tracking pregnancy milestones. It helps in:
Understanding the current stage of pregnancy.
Planning appointments and tests.
Tracking fetal development milestones.
Sharing progress with family and friends.
Simply input your estimated due date and today's date, and the calculator will provide your current gestational age in weeks.
function calculateWeeksPregnant() {
var dueDateInput = document.getElementById("dueDate");
var currentDateInput = document.getElementById("currentDate");
var resultDisplay = document.getElementById("weeksPregnant");
var resultContainer = document.getElementById("result");
var dueDateStr = dueDateInput.value;
var currentDateStr = currentDateInput.value;
if (!dueDateStr || !currentDateStr) {
alert("Please enter both Estimated Due Date and Today's Date.");
return;
}
var dueDate = new Date(dueDateStr);
var currentDate = new Date(currentDateStr);
// Check if dates are valid
if (isNaN(dueDate.getTime()) || isNaN(currentDate.getTime())) {
alert("Please enter valid dates.");
return;
}
// Ensure current date is not after due date for calculation logic
if (currentDate > dueDate) {
// If today is after the due date, it implies the baby has been born.
// For the purpose of "weeks pregnant", we can consider it as 40 weeks pregnant or more.
// Let's cap it at 40 weeks for simplicity in this context.
resultDisplay.textContent = "40+"; // Or a specific message like "Baby Arrived!"
resultContainer.style.display = "block";
resultContainer.style.backgroundColor = "#28a745"; // Keep success green
return;
}
var timeDiff = dueDate.getTime() – currentDate.getTime();
var daysRemaining = Math.ceil(timeDiff / (1000 * 3600 * 24));
var totalGestationDays = 280; // Standard 40 weeks
var calculatedGestationDays = totalGestationDays – daysRemaining;
if (calculatedGestationDays dueDate check,
// but as a failsafe.
resultDisplay.textContent = "0";
} else {
var weeks = Math.floor(calculatedGestationDays / 7);
var days = calculatedGestationDays % 7;
resultDisplay.textContent = weeks + (days > 0 ? "." + days : "");
}
resultContainer.style.display = "block";
}
// Set default dates for user convenience
window.onload = function() {
var today = new Date();
var dd = String(today.getDate()).padStart(2, '0');
var mm = String(today.getMonth() + 1).padStart(2, '0'); // January is 0!
var yyyy = today.getFullYear();
var currentDateInput = document.getElementById("currentDate");
currentDateInput.value = yyyy + '-' + mm + '-' + dd;
// Calculate a sample due date (e.g., 40 weeks from today as a starting point for the input)
// This is just for pre-filling the example, the calculation uses the actual entered dates.
var sampleDueDate = new Date(today);
sampleDueDate.setDate(today.getDate() + 280); // Add 40 weeks
var edd_dd = String(sampleDueDate.getDate()).padStart(2, '0');
var edd_mm = String(sampleDueDate.getMonth() + 1).padStart(2, '0');
var edd_yyyy = sampleDueDate.getFullYear();
var dueDateInput = document.getElementById("dueDate");
dueDateInput.value = edd_yyyy + '-' + edd_mm + '-' + edd_dd;
// Optional: trigger calculation on load if default dates are set
// calculateWeeksPregnant();
};