Determine your current pregnancy stage based on your Last Menstrual Period (LMP) or Estimated Due Date (EDD).
Understanding Pregnancy Milestones and Calculations
Pregnancy is a significant journey, and understanding your progress is crucial. This calculator helps you determine how many weeks pregnant you are, a standard measure used by healthcare providers to track fetal development and manage your prenatal care.
How the Calculation Works:
Pregnancy dating typically starts from the first day of your last menstrual period (LMP). While conception usually occurs about two weeks after the LMP, the 40-week gestation period is calculated from the LMP. This means the first two weeks of your "pregnancy" are dated before conception actually happens.
From LMP: If you input your LMP, the calculator determines the number of days between your LMP and today's date, then converts it into weeks and days. A full-term pregnancy is considered 40 weeks (280 days) from the LMP.
From EDD: If you input your Estimated Due Date (EDD), the calculator determines the number of days remaining until your EDD or the number of days past your EDD. This is useful if your LMP is uncertain or you are using a date provided by an ultrasound.
Why This Matters:
Knowing your gestational age is essential for several reasons:
Fetal Development: It allows you to understand what developmental milestones your baby is likely reaching at each stage.
Medical Appointments: Healthcare providers use this information to schedule prenatal visits, ultrasounds, and screenings.
Preparation: It helps you anticipate major changes in your body and prepare for the arrival of your baby.
Using the Calculator:
To get the most accurate results:
Enter the first day of your last menstrual period (LMP) for the most common dating method.
Alternatively, if you have an Estimated Due Date (EDD) from your doctor or an ultrasound, you can enter that.
The calculator will then display your current gestational age in weeks and days, and indicate if you are approaching, at, or past your due date.
function calculatePregnancyWeeks() {
var lmpInput = document.getElementById("lmpDate");
var eddInput = document.getElementById("eddDate");
var resultDiv = document.getElementById("result");
var lmpDate = lmpInput.value;
var eddDate = eddInput.value;
var today = new Date();
today.setHours(0, 0, 0, 0); // Normalize today's date to midnight
var weeks = 0;
var days = 0;
var message = "";
var errorMessage = "";
if (lmpDate && eddDate) {
errorMessage = "Please enter either your LMP date OR your EDD date, not both.";
} else if (lmpDate) {
var lmp = new Date(lmpDate);
lmp.setHours(0, 0, 0, 0); // Normalize LMP to midnight
if (isNaN(lmp.getTime())) {
errorMessage = "Invalid LMP date entered. Please use YYYY-MM-DD format.";
} else if (lmp > today) {
errorMessage = "LMP date cannot be in the future.";
} else {
var timeDiff = today.getTime() – lmp.getTime();
var daysDiff = Math.floor(timeDiff / (1000 * 60 * 60 * 24));
weeks = Math.floor(daysDiff / 7);
days = daysDiff % 7;
message = "You are approximately " + weeks + " weeks and " + days + " days pregnant.";
var eddFromLmp = new Date(lmp);
eddFromLmp.setDate(eddFromLmp.getDate() + 280); // 40 weeks * 7 days/week
if (today.getTime() < eddFromLmp.getTime()) {
var daysRemaining = Math.floor((eddFromLmp.getTime() – today.getTime()) / (1000 * 60 * 60 * 24));
message += " Your estimated due date is in " + daysRemaining + " days.";
} else if (today.getTime() === eddFromLmp.getTime()) {
message += " Today is your estimated due date!";
} else {
var daysOverdue = Math.floor((today.getTime() – eddFromLmp.getTime()) / (1000 * 60 * 60 * 24));
message += " You are " + daysOverdue + " days past your estimated due date.";
}
}
} else if (eddDate) {
var edd = new Date(eddDate);
edd.setHours(0, 0, 0, 0); // Normalize EDD to midnight
if (isNaN(edd.getTime())) {
errorMessage = "Invalid EDD date entered. Please use YYYY-MM-DD format.";
} else if (edd < today) {
var daysPast = Math.floor((today.getTime() – edd.getTime()) / (1000 * 60 * 60 * 24));
message = "You are approximately " + daysPast + " days past your estimated due date.";
var lmpFromEdd = new Date(edd);
lmpFromEdd.setDate(lmpFromEdd.getDate() – 280); // 40 weeks * 7 days/week
var timeDiff = today.getTime() – lmpFromEdd.getTime();
var daysDiff = Math.floor(timeDiff / (1000 * 60 * 60 * 24));
weeks = Math.floor(daysDiff / 7);
days = daysDiff % 7;
message += " This corresponds to approximately " + weeks + " weeks and " + days + " days of pregnancy.";
} else if (edd.getTime() === today.getTime()) {
message = "Today is your estimated due date!";
var lmpFromEdd = new Date(edd);
lmpFromEdd.setDate(lmpFromEdd.getDate() – 280); // 40 weeks * 7 days/week
var timeDiff = today.getTime() – lmpFromEdd.getTime();
var daysDiff = Math.floor(timeDiff / (1000 * 60 * 60 * 24));
weeks = Math.floor(daysDiff / 7);
days = daysDiff % 7;
message += " This means you are approximately " + weeks + " weeks and " + days + " days pregnant.";
}
else {
var daysRemaining = Math.floor((edd.getTime() – today.getTime()) / (1000 * 60 * 60 * 24));
message = "Your estimated due date is in " + daysRemaining + " days.";
var lmpFromEdd = new Date(edd);
lmpFromEdd.setDate(lmpFromEdd.getDate() – 280); // 40 weeks * 7 days/week
var timeDiff = today.getTime() – lmpFromEdd.getTime();
var daysDiff = Math.floor(timeDiff / (1000 * 60 * 60 * 24));
weeks = Math.floor(daysDiff / 7);
days = daysDiff % 7;
message += " This corresponds to approximately " + weeks + " weeks and " + days + " days of pregnancy.";
}
} else {
errorMessage = "Please enter your LMP date or EDD date.";
}
if (errorMessage) {
resultDiv.style.color = "#dc3545"; // Red for errors
resultDiv.style.backgroundColor = "#f8d7da";
resultDiv.style.borderColor = "#f5c6cb";
resultDiv.innerHTML = errorMessage;
} else {
resultDiv.style.color = "#003a7c"; // Dark blue for results
resultDiv.style.backgroundColor = "#e6f2ff";
resultDiv.style.borderColor = "#004a99";
resultDiv.innerHTML = message;
}
}