Pregnancy Week Calculator

Enter your Last Menstrual Period (LMP) start date or a known Due Date to estimate your current pregnancy week, due date, and trimester.

Last Menstrual Period (LMP) Start Date:

Known Due Date (if LMP is unknown):

Today's Date (or date you want to calculate for):

// Set default for currentDate input to today's date document.addEventListener('DOMContentLoaded', function() { var today = new Date(); var dd = String(today.getDate()).padStart(2, '0'); var mm = String(today.getMonth() + 1).padStart(2, '0'); //January is 0! var yyyy = today.getFullYear(); document.getElementById('currentDate').value = yyyy + '-' + mm + '-' + dd; }); function calculatePregnancyWeeks() { var lmpDateStr = document.getElementById('lastMenstrualPeriodDate').value; var knownDueDateStr = document.getElementById('knownDueDate').value; var currentDateStr = document.getElementById('currentDate').value; var resultDiv = document.getElementById('pregnancyResult'); resultDiv.innerHTML = "; // Clear previous results var lmpDate, knownDueDate, currentDate; // Parse current date if (currentDateStr) { currentDate = new Date(currentDateStr + 'T00:00:00'); // Ensure UTC for consistent date math } else { resultDiv.innerHTML = 'Please enter Today\'s Date.'; return; } // Determine the base LMP date for calculation if (lmpDateStr) { lmpDate = new Date(lmpDateStr + 'T00:00:00'); } else if (knownDueDateStr) { knownDueDate = new Date(knownDueDateStr + 'T00:00:00'); // Calculate LMP from known due date (Due Date – 280 days) lmpDate = new Date(knownDueDate.getTime() – (280 * 24 * 60 * 60 * 1000)); } else { resultDiv.innerHTML = 'Please enter either your Last Menstrual Period Start Date or a Known Due Date.'; return; } // Validate dates if (isNaN(lmpDate.getTime()) || isNaN(currentDate.getTime())) { resultDiv.innerHTML = 'Please enter valid dates.'; return; } // Calculate Estimated Due Date (LMP + 280 days) var estimatedDueDate = new Date(lmpDate.getTime() + (280 * 24 * 60 * 60 * 1000)); // Calculate days pregnant from LMP to current date var timeDiffCurrentToLMP = currentDate.getTime() – lmpDate.getTime(); var daysPregnant = Math.floor(timeDiffCurrentToLMP / (1000 * 60 * 60 * 24)); // Handle cases where current date is before LMP if (daysPregnant = 0 && currentPregnancyWeek = 13 && currentPregnancyWeek = 27 && currentPregnancyWeek = 40) { // Week 41+ trimester = 'Post-term or Due Date Passed'; } else { trimester = 'Not yet pregnant or invalid date range'; } // Calculate days remaining until due date var timeDiffDueToCurrent = estimatedDueDate.getTime() – currentDate.getTime(); var daysRemaining = Math.ceil(timeDiffDueToCurrent / (1000 * 60 * 60 * 24)); // Format dates for display var options = { year: 'numeric', month: 'long', day: 'numeric' }; var formattedLMP = lmpDate.toLocaleDateString('en-US', options); var formattedEstimatedDueDate = estimatedDueDate.toLocaleDateString('en-US', options); var resultHTML = '

Your Pregnancy Details:

'; resultHTML += 'Estimated Due Date: ' + formattedEstimatedDueDate + "; resultHTML += 'Current Pregnancy Week: Week ' + (currentPregnancyWeek + 1) + ' and ' + daysIntoCurrentWeek + ' day(s)'; resultHTML += 'Current Trimester: ' + trimester + "; if (daysRemaining > 0) { resultHTML += 'Days Remaining Until Due Date: ' + daysRemaining + ' days'; } else if (daysRemaining === 0) { resultHTML += 'Due Date: Today!'; } else { resultHTML += 'Days Past Due Date: ' + Math.abs(daysRemaining) + ' days'; } resultHTML += '(Calculated from LMP: ' + formattedLMP + ')'; resultDiv.innerHTML = resultHTML; } .pregnancy-calculator-container { background-color: #f9f9f9; border: 1px solid #ddd; padding: 20px; border-radius: 8px; max-width: 600px; margin: 20px auto; font-family: Arial, sans-serif; box-shadow: 0 2px 4px rgba(0,0,0,0.1); } .pregnancy-calculator-container h2 { color: #333; text-align: center; margin-bottom: 20px; font-size: 1.8em; } .pregnancy-calculator-container p { color: #666; line-height: 1.6; margin-bottom: 15px; } .calculator-input-group { margin-bottom: 15px; } .calculator-input-group label { display: block; margin-bottom: 5px; font-weight: bold; color: #555; } .calculator-input-group input[type="date"] { width: calc(100% – 22px); /* Adjust for padding and border */ padding: 10px; border: 1px solid #ccc; border-radius: 4px; box-sizing: border-box; font-size: 1em; } .pregnancy-calculator-container button { background-color: #4CAF50; color: white; padding: 12px 20px; border: none; border-radius: 4px; cursor: pointer; font-size: 1.1em; width: 100%; margin-top: 10px; transition: background-color 0.3s ease; } .pregnancy-calculator-container button:hover { background-color: #45a049; } .calculator-result { margin-top: 25px; padding: 15px; border: 1px solid #e0e0e0; border-radius: 4px; background-color: #eaf7ea; color: #333; font-size: 1.1em; } .calculator-result h3 { color: #222; margin-top: 0; margin-bottom: 10px; font-size: 1.4em; } .calculator-result p { margin: 8px 0; } .calculator-result strong { color: #222; } .calculator-result .note { font-size: 0.9em; color: #777; margin-top: 15px; } .error-message { color: #d9534f; font-weight: bold; margin-top: 10px; padding: 10px; background-color: #f2dede; border: 1px solid #ebccd1; border-radius: 4px; }

Pregnancy Calculator: Track Your Weeks and Due Date

Understanding your pregnancy timeline is an exciting part of the journey. A pregnancy calculator helps you estimate your due date, determine your current week of pregnancy, and identify which trimester you are in. This tool is based on standard medical calculations, providing a helpful guide as you prepare for your baby's arrival.

How Pregnancy is Dated

Pregnancy is typically dated from the first day of your Last Menstrual Period (LMP), even though conception usually occurs about two weeks later. This method is used because the LMP is a more reliable and easily identifiable date than the exact moment of conception. A full-term pregnancy is considered to be 40 weeks (280 days) from the LMP.

Key Milestones: Trimesters

Pregnancy is divided into three trimesters, each marked by significant developmental changes for the baby and physical changes for the mother:

First Trimester (Weeks 1-13): This period begins with conception and ends around week 13. It's a time of rapid development, with major organs forming. Many women experience morning sickness and fatigue.
Second Trimester (Weeks 14-27): Often considered the "golden trimester," many women find their energy returns and morning sickness subsides. The baby grows significantly, and you might start feeling movements.
Third Trimester (Weeks 28-40+): The final stretch! The baby continues to grow and mature, preparing for birth. You might experience more discomfort as your body prepares for labor.

Using the Pregnancy Week Calculator

Our calculator uses one of two primary inputs to determine your pregnancy timeline:

Last Menstrual Period (LMP) Start Date: This is the most common and accurate way to calculate your due date if you have regular cycles and remember the date.
Known Due Date: If you've had an early ultrasound that provided an estimated due date, you can use this directly. The calculator will then work backward to estimate your LMP.

You will also need to provide Today's Date (or any specific date you wish to calculate for) to determine your current week of pregnancy and how many days remain until your estimated due date.

What the Calculator Provides:

Estimated Due Date: The approximate date your baby is expected to arrive, 40 weeks from your LMP.
Current Pregnancy Week: Your exact week and day of pregnancy as of the "Today's Date" you entered.
Current Trimester: Which of the three trimesters you are currently in.
Days Remaining Until Due Date: A countdown to your baby's estimated arrival.

Example Calculation

Let's say your Last Menstrual Period (LMP) started on January 1, 2024, and you want to know your pregnancy status as of June 15, 2024.

Input LMP: January 1, 2024
Input Today's Date: June 15, 2024

The calculator would then determine:

Estimated Due Date: October 7, 2024 (280 days from Jan 1, 2024)
Current Pregnancy Week: Week 24 and 0 day(s) (165 days from LMP / 7 days per week)
Current Trimester: Second Trimester
Days Remaining Until Due Date: 114 days

Important Considerations

While pregnancy calculators are a fantastic tool for estimation, it's crucial to remember a few things:

Estimates, Not Exacts: Only about 5% of babies are born on their exact due date. Most arrive within a week or two before or after.
Consult Your Doctor: This calculator provides general information. Always consult with your healthcare provider for personalized medical advice, accurate dating, and comprehensive prenatal care.
Irregular Cycles: If you have irregular menstrual cycles, dating your pregnancy based on LMP can be less accurate. An early ultrasound will provide a more precise due date in such cases.

Use this calculator as a fun and informative way to track your pregnancy journey, but always rely on your medical professional for definitive guidance.

Pregnancy Calculator Weeks