Pregnancy is typically measured in weeks, starting from the first day of a woman's last menstrual period (LMP). A full-term pregnancy is considered 40 weeks (280 days) from the LMP. Our calculator uses your estimated due date and today's date to determine how far along you are in your pregnancy, expressed in weeks and days.
How the Calculation Works
The calculator performs a simple date difference calculation. Here's the breakdown:
Target Date: The calculator's primary reference point is the Estimated Due Date (EDD). For a standard 40-week pregnancy, the EDD is exactly 40 weeks (280 days) after the LMP.
Reference Date: We use today's date (or the date you specify) as the reference point.
Calculating Days: The core of the calculation is finding the number of days between the EDD and today's date.
Converting to Weeks and Days: Once the total number of days is calculated, it's converted into weeks and remaining days. There are 7 days in a week.
Formula:
Total Days Difference = EDD – Today's Date
Weeks Pregnant = floor(Total Days Difference / 7)
Days Remaining = Total Days Difference % 7
It's important to note that this calculation is an estimation. The actual conception date can vary, and babies rarely arrive precisely on their due date. For the most accurate information, always consult with your healthcare provider.
When to Use This Calculator
Tracking Progress: To understand how many weeks and days pregnant you are.
Planning: To estimate milestones or plan appointments.
Information: For personal knowledge and to better communicate with healthcare providers.
This tool provides a clear and accessible way to stay informed about your pregnancy journey.
function calculatePregnancyWeeks() {
var dueDateInput = document.getElementById("dueDate");
var currentDateInput = document.getElementById("currentDate");
var resultDiv = document.getElementById("result");
var dueDateStr = dueDateInput.value;
var currentDateStr = currentDateInput.value;
if (!dueDateStr || !currentDateStr) {
resultDiv.innerHTML = "Please enter both your 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())) {
resultDiv.innerHTML = "Invalid date format. Please ensure dates are entered correctly.";
return;
}
// Calculate the difference in milliseconds
var timeDiff = dueDate.getTime() – currentDate.getTime();
// Ensure the current date is not after the due date for a meaningful calculation
if (timeDiff = 40) {
resultMessage = "You are at or past your due date!";
} else {
resultMessage = "You are approximately " + weeks + " weeks and " + days + " days pregnant.";
}
resultDiv.innerHTML = "" + resultMessage + "";
}