Pregnancy Due Date Calculator

Calculator

Enter the first day of your last menstrual period (LMP). The due date is estimated using Naegele's rule (40 weeks from LMP). Only a healthcare provider can confirm your due date.

First day of last menstrual period

Result

Estimated due date

Wed, Oct 22, 2025

Timeline

313 days ago

~84 weeks along (if LMP is correct)

What Is Pregnancy Due Date?

A pregnancy due date calculator provides an estimated timeline for when a baby may be born. The result is useful for a rough calendar reference, but it does not replace prenatal care or a clinician's assessment.

How is the Due Date Calculated?

Most medical professionals and calculators (including this one) use a standard formula known as Naegele's Rule. This formula assumes a standard 28-day menstrual cycle and a 40-week gestation period.

Step 1: Identify the first day of your Last Menstrual Period (LMP).
Step 2: Add one year to that date.
Step 3: Subtract three months.
Step 4: Add seven days.

When to Consult a Doctor

This calculator provides a mathematical estimate. Your healthcare provider may adjust the official due date based on your medical history and early ultrasound measurements.

How To Use the Pregnancy Due Date Calculator

Enter the first day of your last menstrual period (LMP) in the input field.
Review the estimated due date based on Naegele's rule.
Use the Example button to load a sample LMP date, or Reset to clear all fields for a new calculation.
Remember that due dates are estimates; your healthcare provider may adjust it with early ultrasound results.

Due date from the last menstrual period

This pregnancy due date calculator estimates a 40-week due date from the first day of the last menstrual period using Naegele's rule. Cycle variation and clinical dating can change the estimate, so discuss it with a healthcare professional.