9 Month Calculator



Calculating the duration of a pregnancy is a crucial aspect of prenatal care. The 9 Month Calculator provides a convenient tool for estimating the due date based on the first day of the last menstrual period (LMP). This article introduces the calculator, guiding users on its usage, underlying formula, and providing a working HTML and JS code.

How to Use

  1. Input the first day of the last menstrual period (LMP) in the provided text field.
  2. Click the “Calculate” button to initiate the calculation.
  3. The estimated due date will be displayed as the result.


The 9 Month Calculator employs the Naegele’s Rule, a widely accepted formula for estimating the due date. The formula is as follows:


Suppose the LMP is January 1, 2023.


Q: Is the 9 Month Calculator accurate for all pregnancies?

A: While the Naegele’s Rule is a standard method, individual variations may occur. Consult with healthcare professionals for personalized advice.

Q: Can the calculator predict conception date?

A: No, the calculator estimates the due date based on the first day of the last menstrual period, not the conception date.

Q: What if my menstrual cycle is irregular?

A: For those with irregular cycles, the calculator provides a general estimation. Consult a healthcare provider for a more accurate assessment.

Q: Is it suitable for all pregnancy durations?

A: The calculator is primarily designed for pregnancies close to the standard 280 days. Consult healthcare professionals for precision in other cases.


The 9 Month Calculator offers a quick and accessible way to estimate a pregnancy’s due date. By understanding its usage, formula, and limitations, users can utilize this tool effectively. Always consult healthcare providers for personalized advice.

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