Week Of Pregnancy Calculator



Calculating the week of pregnancy is a crucial aspect of prenatal care. It helps expecting mothers and healthcare professionals track the progression of pregnancy and anticipate important milestones. In this article, we will introduce a comprehensive Week of Pregnancy Calculator along with a working HTML and JavaScript code to facilitate accurate calculations.

How to Use

Using the Week of Pregnancy Calculator is straightforward. Enter the date of the last menstrual period (LMP) in the provided input field. Click the “Calculate” button, and the calculator will determine the current week of pregnancy based on widely accepted medical formulas.


The calculation is based on the Naegele’s Rule, a standard method used by healthcare professionals. The formula is as follows:


Consider a scenario where the LMP is January 1, 2023. Applying the formula:

This yields the estimated due date, and subsequently, the current week of pregnancy.


Q1: What is Naegele’s Rule?

Naegele’s Rule is a standard method for estimating the due date by adding 280 days (or 40 weeks) to the first day of the last menstrual period.

Q2: Can the calculator be used for irregular menstrual cycles?

The calculator provides a general estimation based on a standard 28-day cycle. For irregular cycles, it’s advisable to consult with a healthcare professional.

Q3: Is the Week of Pregnancy Calculator accurate?

While the calculator provides a reliable estimate, individual variations exist. Consultation with a healthcare provider is recommended for precise assessments.


The Week of Pregnancy Calculator presented here simplifies the process of determining the current week of pregnancy. It is a valuable tool for expectant mothers to monitor their pregnancy journey and for healthcare professionals to provide optimal care.

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