Calculate exactly how far along you are based on your estimated due date.
How to Use the Pregnancy Week Calculator
Knowing your current week of pregnancy is essential for tracking your baby's development and scheduling prenatal appointments. Most doctors calculate pregnancy based on a 40-week (280-day) timeline starting from the first day of your last menstrual period (LMP). However, if you already have an estimated due date (EDD) provided by an ultrasound or your healthcare provider, this tool allows you to reverse-engineer your current progress.
Understanding Your Results
When you enter your due date, the calculator determines how many days remain until that date. Since a full-term pregnancy is traditionally counted as 280 days, we subtract the remaining days from 280 to find out how many days you have already completed. We then convert those days into weeks and days for a standard clinical reading.
Example Calculation: If your due date is exactly 20 weeks (140 days) from today, the calculator recognizes that you are halfway through your journey. It will display your status as 20 weeks 0 days pregnant.
Trimester Breakdown
Trimester
Time Frame
Key Milestones
First Trimester
Weeks 1 – 12
Organ formation, heartbeat begins.
Second Trimester
Weeks 13 – 26
Baby's movement felt, gender often revealed.
Third Trimester
Weeks 27 – 40
Rapid weight gain, lung maturation.
Why Monitoring Pregnancy by Week Matters
Every week of pregnancy brings significant changes to both the mother and the fetus. For instance, at week 8, the baby is technically a fetus and all major organs have begun to form. By week 24, the baby reaches the "point of viability." Tracking your specific week helps you stay informed about which symptoms are normal and which tests (like the glucose screening or anatomy scan) should be scheduled.
function calculatePregnancy() {
var dueDateValue = document.getElementById("dueDateInput").value;
var resultDiv = document.getElementById("pregResult");
var resultText = document.getElementById("resultText");
if (!dueDateValue) {
alert("Please select a valid due date.");
return;
}
var dueDate = new Date(dueDateValue);
var today = new Date();
// Reset time to midnight for accurate day calculation
today.setHours(0, 0, 0, 0);
dueDate.setHours(0, 0, 0, 0);
// Difference in milliseconds
var diffTime = dueDate – today;
// Convert to days
var diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24));
if (diffDays < -14) {
resultText.innerHTML = "Congratulations!
Based on this due date, your baby has likely already arrived!
";
resultDiv.style.display = "block";
return;
}
if (diffDays > 290) {
resultText.innerHTML = "Check your date
The date entered is more than 40 weeks away. Are you sure about the year?
";
resultDiv.style.display = "block";
return;
}
// Pregnancy is 280 days
var daysPregnant = 280 – diffDays;
if (daysPregnant < 0) {
resultText.innerHTML = "Very Early Days
You are currently in the very first days of your journey (approx. week 0).
";
} else {
var weeks = Math.floor(daysPregnant / 7);
var remainingDays = daysPregnant % 7;
var trimester = "";
if (weeks < 13) {
trimester = "First Trimester";
} else if (weeks < 27) {
trimester = "Second Trimester";
} else {
trimester = "Third Trimester";
}
var html = "You are " + weeks + " weeks and " + remainingDays + " days pregnant.";
html += "
";
html += "Trimester: " + trimester + "";
html += "Days until due date: " + (diffDays > 0 ? diffDays : 0) + " days";
if (weeks >= 37) {
html += "Status: Your baby is considered full-term!";
} else if (weeks >= 18 && weeks <= 22) {
html += "Status: It's usually time for your mid-pregnancy anatomy ultrasound.";
}
html += "