Enter either your Last Menstrual Period (LMP) date OR your Estimated Due Date (EDD) from an ultrasound to calculate key pregnancy milestones.
Your Pregnancy Milestones:
Estimated Due Date:
Last Menstrual Period (LMP):
Approximate Conception Date:
Current Gestational Age:
First Trimester Ends Around:
Second Trimester Ends Around:
function calculateGestation() {
var lmpDateStr = document.getElementById('lmpDate').value;
var eddDateStr = document.getElementById('eddDate').value;
var resultDiv = document.getElementById('gestationResult');
var displayEDD = document.getElementById('displayEDD');
var displayLMP = document.getElementById('displayLMP');
var displayConception = document.getElementById('displayConception');
var displayCurrentGestation = document.getElementById('displayCurrentGestation');
var displayFirstTrimester = document.getElementById('displayFirstTrimester');
var displaySecondTrimester = document.getElementById('displaySecondTrimester');
var lmp, edd, conception;
// Helper function to format date
function formatDate(date) {
if (!date || isNaN(date.getTime())) {
return 'N/A';
}
return date.toLocaleDateString('en-US', { year: 'numeric', month: 'long', day: 'numeric' });
}
// Prioritize LMP if provided
if (lmpDateStr) {
lmp = new Date(lmpDateStr + 'T00:00:00'); // Add T00:00:00 to ensure UTC interpretation for consistency
if (isNaN(lmp.getTime())) {
resultDiv.style.display = 'block';
displayEDD.textContent = 'Invalid LMP Date.';
displayLMP.textContent = ";
displayConception.textContent = ";
displayCurrentGestation.textContent = ";
displayFirstTrimester.textContent = ";
displaySecondTrimester.textContent = ";
return;
}
// Calculate EDD (LMP + 280 days)
edd = new Date(lmp.getTime());
edd.setDate(edd.getDate() + 280);
// Calculate Conception Date (LMP + 14 days)
conception = new Date(lmp.getTime());
conception.setDate(conception.getDate() + 14);
} else if (eddDateStr) {
edd = new Date(eddDateStr + 'T00:00:00');
if (isNaN(edd.getTime())) {
resultDiv.style.display = 'block';
displayEDD.textContent = 'Invalid EDD Date.';
displayLMP.textContent = ";
displayConception.textContent = ";
displayCurrentGestation.textContent = ";
displayFirstTrimester.textContent = ";
displaySecondTrimester.textContent = ";
return;
}
// Calculate LMP (EDD – 280 days)
lmp = new Date(edd.getTime());
lmp.setDate(lmp.getDate() – 280);
// Calculate Conception Date (LMP + 14 days)
conception = new Date(lmp.getTime());
conception.setDate(conception.getDate() + 14);
} else {
resultDiv.style.display = 'block';
displayEDD.textContent = 'Please enter either LMP Date or EDD.';
displayLMP.textContent = ";
displayConception.textContent = ";
displayCurrentGestation.textContent = ";
displayFirstTrimester.textContent = ";
displaySecondTrimester.textContent = ";
return;
}
// Calculate Trimester End Dates (based on LMP)
var firstTrimesterEnd = new Date(lmp.getTime());
firstTrimesterEnd.setDate(firstTrimesterEnd.getDate() + (13 * 7) + 6); // End of 13 weeks (13w6d)
var secondTrimesterEnd = new Date(lmp.getTime());
secondTrimesterEnd.setDate(secondTrimesterEnd.getDate() + (26 * 7) + 6); // End of 26 weeks (26w6d)
// Calculate Current Gestational Age
var today = new Date();
today.setHours(0, 0, 0, 0); // Normalize today's date to start of day
var lmpNormalized = new Date(lmp.getFullYear(), lmp.getMonth(), lmp.getDate()); // Normalize LMP to start of day
var diff_ms = today.getTime() – lmpNormalized.getTime();
var diff_days = Math.floor(diff_ms / (1000 * 60 * 60 * 24));
var currentWeeks = 0;
var currentDays = 0;
if (diff_days >= 0) { // Only calculate if LMP is in the past or today
currentWeeks = Math.floor(diff_days / 7);
currentDays = diff_days % 7;
} else {
// If LMP is in the future, gestational age is 0 weeks 0 days or negative
currentWeeks = 0;
currentDays = 0;
}
// Display results
displayEDD.textContent = formatDate(edd);
displayLMP.textContent = formatDate(lmp);
displayConception.textContent = formatDate(conception);
displayCurrentGestation.textContent = currentWeeks + ' weeks, ' + currentDays + ' days';
displayFirstTrimester.textContent = formatDate(firstTrimesterEnd);
displaySecondTrimester.textContent = formatDate(secondTrimesterEnd);
resultDiv.style.display = 'block';
}
Understanding the Gestation Calculator Wheel
A gestation calculator wheel, often referred to as a pregnancy wheel or due date calculator, is a simple yet powerful tool used by expectant parents and healthcare providers to estimate key dates during pregnancy. While traditional wheels are physical discs, this online version provides the same essential information digitally.
How It Works
The calculator primarily relies on two pieces of information:
- Last Menstrual Period (LMP): This is the first day of your last period. Pregnancy is typically calculated as 40 weeks (280 days) from the LMP, even though conception usually occurs about two weeks later. This method is most accurate if your menstrual cycles are regular (around 28 days).
- Estimated Due Date (EDD) from Ultrasound: Early ultrasounds (especially in the first trimester) can provide a very accurate estimated due date by measuring the size of the fetus. If you have an EDD from an ultrasound, the calculator can work backward to estimate your LMP and other dates.
You only need to enter one of these dates. The calculator will then use standard pregnancy duration (280 days) to determine the others.
What Information Does It Provide?
- Estimated Due Date (EDD): The most anticipated date for any expectant parent, indicating when your baby is likely to arrive.
- Last Menstrual Period (LMP): If you provided an EDD, the calculator will estimate your LMP.
- Approximate Conception Date: This is typically around two weeks after your LMP, when ovulation and fertilization are most likely to occur.
- Current Gestational Age: Based on today's date and your LMP, this tells you how many weeks and days pregnant you currently are.
- Trimester End Dates: Pregnancy is divided into three trimesters, each marking significant developmental stages. Knowing these dates can help you anticipate changes and medical appointments.
- First Trimester: Weeks 1-13. A period of rapid development, often accompanied by early pregnancy symptoms.
- Second Trimester: Weeks 14-26. Often called the "golden trimester" as many early symptoms subside and energy levels may increase.
- Third Trimester: Weeks 27-40. The final stretch, focusing on growth and preparation for birth.
Why is Accurate Dating Important?
Accurate dating of your pregnancy is crucial for several reasons:
- Monitoring Fetal Growth: It helps healthcare providers assess if the baby is growing at an expected rate.
- Scheduling Tests and Screenings: Many prenatal tests are time-sensitive and need to be performed within specific gestational windows.
- Planning for Delivery: Knowing the EDD helps in planning for labor and delivery, and identifying if a pregnancy is post-term.
- Emotional Preparedness: For parents, having these dates helps in preparing mentally and practically for the baby's arrival.
Important Note:
While this calculator provides useful estimates, it is not a substitute for professional medical advice. Always consult with your doctor or healthcare provider for personalized guidance regarding your pregnancy. Due dates are estimates, and only about 5% of babies are born exactly on their due date.