Calculate your estimated due date based on your Last Menstrual Period (LMP) or conception date.
Your Estimated Due Date:
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Understanding Pregnancy Dating
Pregnancy is typically measured in weeks, starting from the first day of a woman's last menstrual period (LMP). This method, known as Gestational Age, is a standard convention used by healthcare providers to track pregnancy progress and estimate the due date. While conception usually occurs about two weeks after the LMP, the gestational age calculation begins from the LMP for simplicity and consistency.
A full-term pregnancy is considered to be 40 weeks (280 days) from the first day of the LMP. This calculator helps you estimate your due date and current gestational age based on either your LMP or an estimated conception date.
How the Calculation Works:
Using LMP: The most common method is to add 40 weeks (280 days) to the first day of your LMP. This is often referred to as Naegele's Rule.
Using Conception Date: If you know your estimated conception date, the calculation is slightly different. Pregnancy is considered 38 weeks (266 days) from the date of conception.
Why Use This Calculator?
Planning: Helps you and your partner plan for the arrival of your baby.
Medical Appointments: Provides an estimated timeframe for important prenatal check-ups and screenings.
Understanding Milestones: Allows you to track fetal development milestones throughout your pregnancy.
Peace of Mind: Offers clarity and reduces anxiety about the exact timing of your pregnancy.
Disclaimer: This calculator provides an estimation. The actual date of birth can vary. Always consult with your healthcare provider for accurate medical advice and to confirm your due date.
function calculateDueDate() {
var lmpDateInput = document.getElementById("lmpDate");
var conceptionDateInput = document.getElementById("conceptionDate");
var dueDateDisplay = document.getElementById("dueDateDisplay");
var gestationalAgeDisplay = document.getElementById("gestationalAgeDisplay");
var lmpDateStr = lmpDateInput.value;
var conceptionDateStr = conceptionDateInput.value;
var dueDate = null;
var gestationalAgeWeeks = 0;
var gestationalAgeDays = 0;
var currentDate = new Date();
if (lmpDateStr) {
var lmpDate = new Date(lmpDateStr);
if (!isNaN(lmpDate.getTime())) {
// Naegele's Rule: Add 40 weeks (280 days) to LMP
var dueDateFromLMP = new Date(lmpDate);
dueDateFromLMP.setDate(dueDateFromLMP.getDate() + 280);
dueDate = dueDateFromLMP;
// Calculate gestational age from LMP to current date
var timeDiff = currentDate.getTime() – lmpDate.getTime();
var daysDiff = Math.floor(timeDiff / (1000 * 60 * 60 * 24));
gestationalAgeWeeks = Math.floor(daysDiff / 7);
gestationalAgeDays = daysDiff % 7;
}
} else if (conceptionDateStr) {
var conceptionDate = new Date(conceptionDateStr);
if (!isNaN(conceptionDate.getTime())) {
// Add 38 weeks (266 days) to conception date
var dueDateFromConception = new Date(conceptionDate);
dueDateFromConception.setDate(dueDateFromConception.getDate() + 266);
dueDate = dueDateFromConception;
// Calculate gestational age from conception to current date
var timeDiff = currentDate.getTime() – conceptionDate.getTime();
var daysDiff = Math.floor(timeDiff / (1000 * 60 * 60 * 24));
gestationalAgeWeeks = Math.floor(daysDiff / 7);
gestationalAgeDays = daysDiff % 7;
}
}
if (dueDate) {
var options = { year: 'numeric', month: 'long', day: 'numeric' };
dueDateDisplay.textContent = dueDate.toLocaleDateString(undefined, options);
if (gestationalAgeWeeks >= 0) {
gestationalAgeDisplay.textContent = "Current Gestational Age: " + gestationalAgeWeeks + " weeks and " + gestationalAgeDays + " days";
} else {
gestationalAgeDisplay.textContent = "Current Gestational Age: Not yet started";
}
} else {
dueDateDisplay.textContent = "Please enter a valid date.";
gestationalAgeDisplay.textContent = "";
}
}