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Formula guide

Pregnancy Due Date Calculator formula

The standard due date estimate adds 280 days, or 40 weeks, to the first day of the last menstrual period. This is a common medical convention for estimating a due date in uncomplicated pregnancies.

How to read the formula

The formula section explains the math logic behind the calculator result. On Mega Calculators, the formula is written in plain English so users can understand the relationship between the main inputs, not just copy numbers into a form.

For pregnancy due date calculator, the most important step is understanding how each input changes the output. Small changes in time, rate, quantity, or conversion values can materially change the final result.

This page is meant to help with learning and comparison. For professional or regulated calculations, always confirm the result with an official document, lender, employer, school, or medical professional when relevant.

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Example pages related to this formula

Pregnancy Due Date Calculator basic example
See a basic pregnancy due date calculator scenario using the default inputs on Mega Calculators.
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