Pregnancy Month Calculator by Week
Use this calculator to convert your current pregnancy week into an approximate month. While pregnancy is most accurately tracked in weeks, this tool can help you understand which month of pregnancy you are in.
function calculatePregnancyMonths() {
var weeksInput = document.getElementById("weeksPregnantInput").value;
var weeks = parseFloat(weeksInput);
var resultDiv = document.getElementById("monthsResult");
if (isNaN(weeks) || weeks 42) {
resultDiv.innerHTML = "Please enter a valid number of weeks (1-42).";
return;
}
// Standard pregnancy is 40 weeks, often divided into 9 months.
// Average weeks per month = 40 weeks / 9 months = ~4.44 weeks/month
// Or, more commonly, 52 weeks / 12 months = ~4.33 weeks/month.
// We'll use 4.33 for a more general conversion, and also provide a rounded month.
var monthsPrecise = weeks / 4.33;
var monthsRounded = Math.ceil(weeks / 4.33); // Round up to the next full month
// Adjust for common pregnancy month mapping (e.g., 1-4 weeks = Month 1, 5-8 weeks = Month 2, etc.)
// This is a common way to present it, though not mathematically precise for every week.
var commonMonth;
if (weeks >= 1 && weeks = 5 && weeks = 9 && weeks = 14 && weeks = 18 && weeks = 22 && weeks = 27 && weeks = 31 && weeks = 36 && weeks 40) { commonMonth = 10; } // Post-term
resultDiv.innerHTML = `
If you are
${weeks} weeks pregnant:
You are approximately
${monthsPrecise.toFixed(1)} months pregnant.
This means you are in your
Month ${commonMonth} of pregnancy.
`;
}
.pregnancy-month-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
background-color: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 25px;
max-width: 600px;
margin: 20px auto;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
color: #333;
}
.pregnancy-month-calculator-container h2 {
color: #e91e63; /* Pink for pregnancy theme */
text-align: center;
margin-bottom: 20px;
font-size: 1.8em;
}
.pregnancy-month-calculator-container p {
line-height: 1.6;
margin-bottom: 15px;
}
.calculator-form .form-group {
margin-bottom: 18px;
}
.calculator-form label {
display: block;
margin-bottom: 8px;
font-weight: bold;
color: #555;
}
.calculator-form input[type="number"] {
width: calc(100% – 22px);
padding: 12px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 1em;
box-sizing: border-box;
}
.calculator-form button {
background-color: #e91e63; /* Pink */
color: white;
padding: 12px 25px;
border: none;
border-radius: 5px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
display: block;
width: 100%;
margin-top: 20px;
}
.calculator-form button:hover {
background-color: #c2185b; /* Darker pink */
}
.result-container {
background-color: #fff0f5; /* Light pink */
border: 1px solid #f8bbd0;
border-radius: 8px;
padding: 15px 20px;
margin-top: 25px;
font-size: 1.1em;
color: #333;
}
.result-container p {
margin: 8px 0;
}
.result-container p strong {
color: #e91e63;
}
.result-container .error {
color: #d32f2f; /* Red for errors */
font-weight: bold;
}
Understanding Pregnancy Weeks and Months
Pregnancy is typically measured from the first day of your last menstrual period (LMP), even though conception usually occurs about two weeks later. This method results in a full-term pregnancy lasting approximately 40 weeks, or 280 days.
Why the Confusion Between Weeks and Months?
The discrepancy often arises because months don't perfectly divide into four-week segments. While it's common to say "four weeks equals one month," this isn't entirely accurate. Most calendar months have more than four weeks (e.g., 30 or 31 days, which is 4 weeks and 2-3 days). This means that over the course of a 9-month pregnancy, you'll accumulate a few extra weeks.
For medical professionals, tracking pregnancy in weeks is more precise because it allows for consistent monitoring of fetal development and maternal changes. However, for expectant parents, converting weeks to months can be helpful for communicating progress to friends and family.
How the Conversion Works
Our calculator uses an average conversion rate (approximately 4.33 weeks per month) to give you a precise decimal month. We also provide a common rounded month based on typical pregnancy month groupings, which helps align with how many people informally track their pregnancy.
Pregnancy Trimesters
Pregnancy is also divided into three trimesters, each lasting about three months or 13-14 weeks:
- First Trimester: Week 1 to Week 13. This is a period of rapid development, where all major organs begin to form.
- Second Trimester: Week 14 to Week 27. Often considered the "golden trimester," as many early pregnancy symptoms subside and energy levels may increase.
- Third Trimester: Week 28 to Week 40 (or birth). The baby grows rapidly, gaining weight and preparing for birth.
Examples:
- If you are 8 weeks pregnant: You are approximately 1.8 months pregnant, which means you are in your Month 2.
- If you are 13 weeks pregnant: You are approximately 3.0 months pregnant, which means you are in your Month 3.
- If you are 20 weeks pregnant: You are approximately 4.6 months pregnant, which means you are in your Month 5.
- If you are 36 weeks pregnant: You are approximately 8.3 months pregnant, which means you are in your Month 9.
Remember, these conversions are approximations. Always refer to your healthcare provider for the most accurate information regarding your pregnancy progress.