Enter your Last Menstrual Period (LMP) date or your Estimated Due Date (EDD) to find out your current pregnancy week, remaining days, and more.
(Optional, if LMP is unknown)
function calculatePregnancy() {
var lmpDateInput = document.getElementById('lastMenstrualPeriodDate').value;
var eddDateInput = document.getElementById('estimatedDueDate').value;
var resultDiv = document.getElementById('pregnancyResult');
resultDiv.innerHTML = "; // Clear previous results
var lmpDate, eddDate;
var today = new Date();
today.setHours(0, 0, 0, 0); // Normalize today's date to start of day
var daysPregnant = 0;
var daysRemaining = 0;
var calculatedEdd = null;
var calculatedLmp = null;
// Prioritize LMP if provided
if (lmpDateInput) {
lmpDate = new Date(lmpDateInput);
lmpDate.setHours(0, 0, 0, 0); // Normalize date to start of day
if (isNaN(lmpDate.getTime())) {
resultDiv.innerHTML = 'Please enter a valid Last Menstrual Period date.';
return;
}
if (lmpDate > today) {
resultDiv.innerHTML = 'LMP date cannot be in the future.';
return;
}
var timeDiffLMP = today.getTime() – lmpDate.getTime();
daysPregnant = Math.floor(timeDiffLMP / (1000 * 60 * 60 * 24));
// Calculate EDD from LMP (280 days)
calculatedEdd = new Date(lmpDate.getTime() + (280 * 24 * 60 * 60 * 1000));
calculatedEdd.setHours(0, 0, 0, 0);
var timeDiffToEdd = calculatedEdd.getTime() – today.getTime();
daysRemaining = Math.ceil(timeDiffToEdd / (1000 * 60 * 60 * 24));
calculatedLmp = lmpDate;
} else if (eddDateInput) {
eddDate = new Date(eddDateInput);
eddDate.setHours(0, 0, 0, 0); // Normalize date to start of day
if (isNaN(eddDate.getTime())) {
resultDiv.innerHTML = 'Please enter a valid Estimated Due Date.';
return;
}
if (eddDate < today) {
resultDiv.innerHTML = 'Estimated Due Date cannot be in the past.';
return;
}
calculatedEdd = eddDate;
var timeDiffToEdd = calculatedEdd.getTime() – today.getTime();
daysRemaining = Math.ceil(timeDiffToEdd / (1000 * 60 * 60 * 24));
daysPregnant = 280 – daysRemaining;
// Calculate LMP from EDD (280 days prior)
calculatedLmp = new Date(eddDate.getTime() – (280 * 24 * 60 * 60 * 1000));
calculatedLmp.setHours(0, 0, 0, 0);
} else {
resultDiv.innerHTML = 'Please enter either your Last Menstrual Period date or your Estimated Due Date.';
return;
}
if (daysPregnant 294) { // Roughly 42 weeks, beyond typical full-term
resultDiv.innerHTML = 'Based on the dates, your baby may have already arrived! Please check your input dates.';
return;
}
var currentWeek = Math.floor(daysPregnant / 7);
var currentDayOfWeek = daysPregnant % 7;
var trimester = ";
if (currentWeek >= 0 && currentWeek = 14 && currentWeek = 28 && currentWeek 40) {
trimester = 'Post-term (beyond 40 weeks)';
} else {
trimester = 'Pre-conception or very early pregnancy';
}
var options = { year: 'numeric', month: 'long', day: 'numeric' };
var formattedEdd = calculatedEdd ? calculatedEdd.toLocaleDateString('en-US', options) : 'N/A';
var formattedLmp = calculatedLmp ? calculatedLmp.toLocaleDateString('en-US', options) : 'N/A';
var outputHTML = '
Understanding Your Pregnancy Journey: A Week-by-Week Guide
Congratulations on your pregnancy! This incredible journey is filled with anticipation, changes, and milestones. Knowing your current week of pregnancy is crucial for tracking your baby's development, understanding what to expect, and preparing for your due date. Our Week-to-Week Pregnancy Calculator helps you pinpoint exactly where you are in this exciting process.
How Does the Pregnancy Calculator Work?
Our calculator uses standard medical guidelines to estimate your pregnancy week and due date. The most common method for dating a pregnancy is based on the first day of your Last Menstrual Period (LMP). This is because ovulation and conception dates can be difficult to pinpoint precisely, while the LMP is usually a more reliable starting point.
Using Your Last Menstrual Period (LMP): A full-term pregnancy is typically considered to be 40 weeks (280 days) from the first day of your LMP. The calculator takes your LMP date, calculates the number of days that have passed until today, and then converts that into weeks and days. It also projects your Estimated Due Date (EDD) by adding 280 days to your LMP.
Using Your Estimated Due Date (EDD): If you've already had an ultrasound or your doctor has provided you with an EDD, you can use this input instead. The calculator will work backward from your EDD to determine your current pregnancy week and the approximate date of your LMP.
Why is Knowing Your Pregnancy Week Important?
Tracking your pregnancy week by week offers numerous benefits:
Fetal Development: Each week brings new developmental milestones for your baby. Knowing your current week allows you to research and understand what changes are happening inside you.
Maternal Changes: Your body also undergoes significant changes. Understanding your current week helps you anticipate common symptoms, prepare for prenatal appointments, and know when certain tests or screenings are typically performed.
Planning and Preparation: From planning your baby shower to preparing your nursery, knowing your due date and current stage helps you organize and manage your pregnancy journey effectively.
Medical Guidance: Healthcare providers use your pregnancy week to monitor your baby's growth, schedule important ultrasounds, and assess any potential risks or complications.
Understanding Trimesters
Pregnancy is commonly divided into three trimesters, each lasting approximately 13-14 weeks, characterized by distinct developmental stages for the baby and different experiences for the mother:
First Trimester (Weeks 0-13): This period begins with conception and is marked by rapid cell division and the formation of major organs. Many women experience morning sickness, fatigue, and breast tenderness.
Second Trimester (Weeks 14-27): Often called the "golden trimester," many early pregnancy symptoms subside, and energy levels may increase. This is when you might feel your baby's first movements (quickening) and often have your anatomy scan ultrasound.
Third Trimester (Weeks 28-40+): The final stretch! Your baby grows rapidly, gaining weight and preparing for birth. You might experience increased discomfort, Braxton Hicks contractions, and a strong nesting instinct.
Example Calculation:
Let's say your Last Menstrual Period (LMP) started on January 1, 2024. If today's date is June 15, 2024:
Days from LMP to today: Approximately 167 days.
Current Pregnancy Week: 167 days / 7 days/week = 23 weeks and 6 days.
Estimated Due Date: January 1, 2024 + 280 days = October 7, 2024.
Days Remaining Until Due Date: Approximately 114 days.
Current Trimester: Second Trimester.
This calculator provides a helpful estimate, but always consult with your healthcare provider for personalized medical advice and the most accurate dating of your pregnancy.