Calculate your baby's estimated due date using the Naegele's Rule.
Estimated Due Date: —
Understanding EDC and Naegele's Rule
The Estimated Date of Confinement (EDC), also commonly known as the Estimated Due Date (EDD), is a crucial date for expectant parents and healthcare providers. It represents the predicted day your baby is likely to be born. While it's an estimate, it provides a valuable timeline for prenatal care, monitoring fetal development, and preparing for delivery.
What is Naegele's Rule?
The most common method for calculating the EDC is Naegele's Rule. This rule provides a simple way to estimate the due date based on the first day of a woman's last menstrual period (LMP). The rule is as follows:
Add 7 days to the first day of your LMP.
Subtract 3 months from the resulting month.
Add 1 year to the resulting year.
In simpler terms, it's LMP + 9 months + 7 days, or LMP + 40 weeks.
How the Calculator Works:
This calculator automates Naegele's Rule. When you input the first day of your Last Menstrual Period (LMP), the calculator performs the following steps:
It takes the date you entered.
It adds 7 days to this date.
It then subtracts 3 months from the month of the new date.
Finally, it adds 1 year to the year of the new date.
The result is your Estimated Date of Confinement (EDC).
Important Considerations:
Accuracy: Naegele's Rule assumes a regular 28-day menstrual cycle with ovulation occurring around day 14. For individuals with irregular cycles, shorter or longer cycles, or uncertainty about their LMP, this date is an estimate and may not be perfectly accurate.
First Ultrasound: In early pregnancy, a first-trimester ultrasound is often considered the most accurate method for dating a pregnancy.
Term Pregnancy: A full-term pregnancy is typically considered to be between 37 and 42 weeks. Your EDC is an estimate, and babies can be born before or after this date.
Consult Your Doctor: Always discuss your EDC and pregnancy timeline with your healthcare provider. They will confirm the date and provide comprehensive prenatal care.
This calculator is a helpful tool for a quick estimation but should not replace professional medical advice.
function calculateEDC() {
var lmpInput = document.getElementById("lastMenstrualPeriod").value;
var resultDisplay = document.getElementById("edcResult");
if (!lmpInput) {
resultDisplay.textContent = "Please enter your LMP.";
return;
}
var lmpDate = new Date(lmpInput);
var lmpDay = lmpDate.getDate();
var lmpMonth = lmpDate.getMonth(); // 0-indexed (0 = January, 11 = December)
var lmpYear = lmpDate.getFullYear();
// Apply Naegele's Rule: LMP + 9 months + 7 days
// This is equivalent to LMP + 7 days – 3 months + 1 year
var edcDate = new Date(lmpYear, lmpMonth, lmpDay);
// Add 7 days
edcDate.setDate(edcDate.getDate() + 7);
// Subtract 3 months
edcDate.setMonth(edcDate.getMonth() – 3);
// Add 1 year
edcDate.setFullYear(edcDate.getFullYear() + 1);
// Format the date to be more readable (YYYY-MM-DD)
var formattedMonth = (edcDate.getMonth() + 1).toString().padStart(2, '0'); // Month is 0-indexed, add 1
var formattedDay = edcDate.getDate().toString().padStart(2, '0');
var formattedYear = edcDate.getFullYear();
var finalEDC = formattedYear + '-' + formattedMonth + '-' + formattedDay;
resultDisplay.textContent = finalEDC;
}