A pregnancy wheel calculator helps expectant parents and healthcare providers estimate key dates throughout pregnancy, such as the estimated due date (EDD), conception date, and current gestational age. It's a quick and easy way to track your pregnancy journey based on your Last Menstrual Period (LMP) or a known Estimated Due Date.
Calculate from Last Menstrual Period (LMP)
Calculate from Estimated Due Date (EDD)
Understanding Your Pregnancy Dates
The most common method for calculating pregnancy dates is Naegele's Rule, which assumes a 28-day menstrual cycle with ovulation occurring on day 14. According to this rule, pregnancy lasts approximately 280 days (40 weeks) from the first day of your Last Menstrual Period (LMP).
Estimated Due Date (EDD): This is the date your baby is expected to arrive. Only about 5% of babies are born exactly on their due date, but it provides a good target for planning.
Conception Date: This is the approximate date when fertilization likely occurred. It's typically about two weeks after your LMP.
Gestational Age: This refers to how far along your pregnancy is, measured in weeks and days from your LMP.
Trimester Breakdown: Pregnancy is divided into three trimesters, each marking significant developmental stages for the baby and changes for the mother.
First Trimester: From LMP to the end of week 13. This is a period of rapid development for the baby's organs.
Second Trimester: From the start of week 14 to the end of week 27. Often called the "golden trimester," as many early pregnancy symptoms subside.
Third Trimester: From the start of week 28 to the EDD (end of week 40). The baby grows rapidly and prepares for birth.
How to Use This Calculator
This calculator offers two ways to determine your pregnancy milestones:
Using Your Last Menstrual Period (LMP): If you know the exact date of the first day of your last period, enter it into the "Last Menstrual Period (LMP) Date" field and click "Calculate from LMP."
Using Your Estimated Due Date (EDD): If your doctor has already provided you with an Estimated Due Date (perhaps from an early ultrasound), enter it into the "Estimated Due Date (EDD)" field and click "Calculate from EDD."
The calculator will then provide your EDD, estimated conception date, current gestational age, and the start and end dates for each trimester.
Important Considerations
While this calculator provides useful estimates, it's important to remember:
Irregular Cycles: If you have irregular menstrual cycles, the LMP method may not be as accurate.
Early Ultrasound: An early ultrasound (typically between 8-12 weeks) is often the most accurate way to determine gestational age and EDD, as it measures the baby's size directly.
Individual Variation: Every pregnancy is unique. Always confirm your dates and discuss any concerns with your healthcare provider.
function formatDate(date) {
var d = new Date(date),
month = " + (d.getMonth() + 1),
day = " + d.getDate(),
year = d.getFullYear();
if (month.length < 2)
month = '0' + month;
if (day.length < 2)
day = '0' + day;
return [month, day, year].join('/');
}
function addDays(date, days) {
var result = new Date(date);
result.setDate(result.getDate() + days);
return result;
}
function subtractDays(date, days) {
var result = new Date(date);
result.setDate(result.getDate() – days);
return result;
}
function getWeeksAndDays(startDate, endDate) {
var diffTime = endDate.getTime() – startDate.getTime();
if (diffTime < 0) { // If end date is before start date, gestational age is 0
return { weeks: 0, days: 0 };
}
var diffDays = Math.floor(diffTime / (1000 * 60 * 60 * 24));
var weeks = Math.floor(diffDays / 7);
var days = diffDays % 7;
return { weeks: weeks, days: days };
}
function calculateFromLMP() {
var lmpDateStr = document.getElementById("lmpDate").value;
var resultDiv = document.getElementById("pregnancyResult");
resultDiv.innerHTML = ""; // Clear previous results
if (!lmpDateStr) {
resultDiv.innerHTML = "Please enter your Last Menstrual Period (LMP) date to calculate.";
return;
}
var lmp = new Date(lmpDateStr + "T00:00:00"); // Ensure consistent timezone interpretation
// Calculate EDD (LMP + 280 days)
var edd = addDays(lmp, 280);
// Calculate Conception Date (LMP + 14 days)
var conceptionDate = addDays(lmp, 14);
// Calculate Current Gestational Age
var today = new Date();
today.setHours(0, 0, 0, 0); // Normalize today's date to start of day
var gestationalAge = getWeeksAndDays(lmp, today);
// Calculate Trimester Dates
var firstTrimesterEnd = addDays(lmp, (13 * 7) + 6); // End of week 13 (day 6)
var secondTrimesterStart = addDays(lmp, 14 * 7); // Start of week 14
var secondTrimesterEnd = addDays(lmp, (27 * 7) + 6); // End of week 27 (day 6)
var thirdTrimesterStart = addDays(lmp, 28 * 7); // Start of week 28
var output = "